You dress for the crash, not the ride.
Wear your fucking gear.
Start with a used kawasaki ninja 250 (emphasis on used) because you will drop your bike a few times. Trust me, you will.
Also used = cheaper in terms of what the bike will cost you plus insurance.
You buy weak and cheap first because buying an expensive motorcycle right away when it's something you actually might not be into is a stupid move financially. You also get a "weak" bike (250cc is enough to get a 180 pound guy to 100mph - i don't know if that's really "weak") because they are more forgiving. If ever you panic and you hit the throttle on a 250, it will give you some lee way to recover. The acceleration is linear and predictable. It is also is not super instant.
A bike like the ninja zx14 has 1400cc and is a 4 cylinder motorcycle. This means the power and acceleration of the motorcycle are less predictable and much more instant. Some of the power is more specific to a certain power band (the rpm you are at in whatever gear you are in). This means if you hit the throttle too hard, you'll be doing over 150mph within seconds.
Learn to walk, before you run.
Take an MSF course.
After you feel you've ridden the "weak" bike well and have a few months on the saddle. Then you can upgrade to a 500 or 650 cc motorcycle.
You don't have to upgrade. You are not a pussy for staying with 250cc. If that is all you need, and you are happy and comfortable with it, then that is fine. In the end it's getting you from point A to point B. Getting from one red light to another 3 seconds sooner won't help in the grand scheme of things. It might help you get a ticket though.
Just be warned that a 600cc is much much MUCH more powerful than a 650cc bike. Make sure it's a mistake you don't make.
When factoring a bike's potential in terms of speed, torque and horse power you have to also look at how many cylinders a bike has. More cylinders usually means more everything. Alot more. 600cc bikes are either 3 or 4 cylinder and 250, 500 and 650cc are 2 cylinder bikes.
The zx14 (1400cc) and the zx6r (600cc) are both 4 cylinders whereas the 650r (650cc ) is only 2 cylinders.
600cc bikes and above (for crotch rockets - not cruisers) means they are race ready.
They are called crotch ROCKETS for a reason.
Take an MSF course.
The ultimate beginner motorcycle is the kawasaki ninja 250. It's cheap (new or used), has good resale value and has enough oomph to be fun.
From then on you can look at the ninja 500 or the ninja 650 or suzuki sv650.
You can start with 500cc or 650cc if you think you can. I advise against it however. Do not fucking start on anything that is more than 2 cylinders.
For insurance, i've heard good things about State Farm. They charge you depending on the displacement (cc) of your motorcycle. So a used ninja 250 will be quite cheap. Look into it.
Keep in mind that there is a sizing aspect to motorcycles. The most important factor is inseam and not height.
You might be 6 foot 4 but if your inseam is 27 inches, you will have a hard time finding a motorcycle.
Inseam is taken barefoot and it goes from the floor straight up to your family jewels and pressed a bit into the skin.
Don't forget to take a MSF course.
A hayabusa or zx14 only costs around 15grand (all things considered it's not THAT much) but both have a top speed of over 180mph and can get there in less than 10 seconds.
They are the ferrari and lamborghini of the motorcycling world. Treat them with respect. Chances are you will never need bikes this powerful. You don't learn to drive with an f1 car so for motorcycles it's the same.
You might fuck up in a car and skid, or drift or turn or maybe crash but chances are you won't be really hurt (the first time you drive). If you fuck up on a motorcycle there is no drifting or sliding. It's either you stay on the bike or you fall off. There is no airbag or seat belt and being inside a metal container to keep you safe. Motorcycles are basically 500 pound, explosive strapped bicycles with engines.
When you fall, the bike falls too. And a 500 pound super heated metal object flipping through the air at 100 mph is not something you want to mess with. If ever you do fall, try to fall to the left of the motorcycle while having the motorcycle tilt to the right.( Don't fall with the motorcycle. Fall away from it.)
The exhaust is always on the right side and that side tends to be the hottest. The exhaust is always very hot. Be careful.
Falling the other way increases your chances of not being burnt. Keep that in mind.
Also, again, you can get trapped under the motorcycle if you fall wrong.
The friction between your skin and the road becomes a whole lot worse when you are being pinned down by 500 pounds. Keep that in mind too.
Which brings me to my next point.
There are two ways for an accident to hurt you. Blunt physical trauma (hitting the floor, curb or another car) or abrasion (the friction between you and the road = your skin and muscle gets ripped off).
Helmets help with the physical damage. Your helmet should feel somewhat snug. Most people hit the chin area of their helmet when they crash (people tend to fall forward, not backwards) and so a full face helmet is a smart investment. A REALLY smart investment.
However the leather jacket and pants you wear don't usually have protection (some of them do) in terms of blunt damage. It's just a jacket. It will help tremendously with abrasion though. Abrasion is the affect of friction on an object. In this case the road and you.
If you slide doing 60 mph your jeans will take 3-5 seconds of sliding before exposing skin. A good pair of leather pants can last to 12 seconds and beyond. Motorcycle gear is expensive, so factor that into your financing as well.
I advise you to get gloves with protection (they come with built in hard protection against blunt trauma for the wrist and knuckles), boots (with protection such as steel toes and extra rigidity so your foot doesn't twist backwards if you fall ) and a good pair of leather pants and leather jacket.
For the protection under the jacket and pants (which will help tremendously with abrasion), buy an after market protection product such as Velocity Gear's "Juggernaut" Motorcycle Armor Shirt.
The thing about built in protection in certain jackets is that the jacket will never fit you perfectly and even if it does, it will move with the shirt, which can minimize protection.
Just like football players and hockey players wear armor under the shirt. The armor isn't part of the shirt cause then it can be moved out of place.
For helmets try Bell: http://www.thebellstore.com/Helmets/apex.html
Boots: http://www.oxtar-boots.com/ss.html or http://www.oxtar-boots.com/tcsrx.html
http://www.foxcreekleather.com/mensjackets.phtml expensive as fuck but great quality or try http://www.roadgear.com/index.php?page=Product&PHPSESSID=fa6fea377c2e0e95afa40f2a185ea437&id=12 or http://www.tourmaster.com/xcart/product.php?productid=240&cat=3
Armor under jacket: http://highvelocitygear.com/productpages/juggernaut.html
Armor under pants: http://www.bohnarmor.com/catalog/proddetail.php?prod=BGKC (pants part only)
Gloves: http://www.sporttour.com/motorcycle-apparel/Marsee_Race_Glove.html (discontinued but so you get an idea of the style and protection you need)
Get a polar arctic buff for comfort too: http://www.moestackleshop.com/how-to/polar-buff-arctic-buff
You don't need a leather jacket or pants since there is also textile out there. It's not as protective but it's not such a bitch during rain and tends to breathe better.
These are just suggestions. Feel free to look around.
If you're into cruisers or modern classic bikes, take a look at triumph they are a quality brand, pretty popular (more popular = more dealers = more parts = easier to fix a problem with your bike, etc), look really fucking good, are reasonably priced, have great engineering and they make some high quality crotch rockets too.
Harley's sound cool (it is a Harley after all) but they tend to be over priced (50 grand for a motorcycle - really?) and i hear they have many problems. If that's what you're into, then that's cool too. Just be aware that there are many brands to choose from.
Motorcycles are great because they give you something around 50 miles per gallon, are reasonably price (a high end bike costs as much as a low end car)and look good.
When riding, be careful. For one, people are looking for cars, not motorcycles. So they might not see you. It sounds funny, but that's how it happens. It's kind of like how many people walk into moving electric cars. Electric cars make no noise what so ever. So when someone sees it moving towards them, they don't hear a noise. This goes against what they expect (a moving car makes engine noise- right?) and so their mind blocks out the car. It becomes invisible. I have never been hit by an electric car because of this but i almost have. Motorcycles are just invisible period.
So...when riding, pretend you are invisible. Assume that the person might not see you and be prepared. This goes for city riding too.
Imagine the high way as a really big water tank and you are a person swimming in it. The cars and trucks moving are like large boats. As they pass you at high speeds, the wake and current will move you around.
Air is less dense than water, but it is also subject to movement (wind) due to change in pressure and movement of other physical objects.
An 18 wheel truck displaces alot of air. The air in front of it is being pushed away (in 3 dimensions), and the space where the truck was is now a void. So the air will then rush back to where the truck just was.
Imagine doing this at high speeds and you can get an idea of the kind of serious air current we get around a large truck. You have surely been passed on the highway by a car going very fast and felt your car slightly shake when the care passed you. You probably even heard the air it pushed aside.
These air currents are a serious threat to motorcycles. Be careful around trucks and cars on highways, not just because they can't see you but also because the air currents can exert pressure on you and it's not unheard for a motorcyclist to feel as though he is being pulled towards the back or sides of a truck. It is a very abrupt and aggressive pulling motion, so be alert.
Sorry if this was a bit long. I know it was more pessimistic and not so much "thought" but it's good advice that a 21 year old kid should have when learning to ride the first time. Knowing is half the battle, blablabla.
Motorcycles are a great idea, but you need to respect the responsibility and danger that comes with it.
Good luck and ride smart.