It's a safe bet that the situations where you have to fight back will happen maybe once or twice in the average person's life, if that.
The situations where you HAVE to fight back are the ones where you're not fighting- it's self defense.
This is a home invasion, this is you're overseas and someone comes at you with a knife, this is that infamous fucking mugger that's going to kill and rob you.
This shit NORMALLY doesn't happen to people who don't hang out at shitholes and "lead the life" so to speak.
Otherwise, there's a lot of "gray area" ones that we could get into, the infamous "What do i do if 27 ninjas with machine guns come at me" scenarios.
Someone grabs your chick's ass or tells her to fuck herself, someone postures up to you at a bar trying to fight, someone gets out of their car in a road rage incident and comes at you... they're all gray area things in the eyes of the law that might be self defense or they might be assault depending on who the witnesses are and how bad you fuck the guy up (or get fucked up).
It doesn't make you macho. In fact, it might give you some legal ground to stand on if you'd hit him when he came to pushing you.
But then again, maybe not.
You don't want to look like a pussy, I get it. You also don't want to be starting at a judge in a month when you hit the guy, he falls backwards, hits his head on the corner of the desk, and he haemorrhages and dies.
BANG! That's manslaughter bro. Have fun for the next 5 or 10.
And you look like a grownup when you walk away from a fight. I've walked away from some when I knew I was outgunned or outfucked, I've lost many more than I've won. Seriously, don't fucking bother. They're nothing but a hassle.
But, if a guy does put his hands on you...
Go learn to box.
You're not going to learn "tactics" or fighting moves from the internet and even if you could, you'll likely do them all wrong and just ingrain bad habits.
Go to a boxing gym.
For further information, read "The Little black book of violence" and "Meditations on Violence."
The first will tell you how to avoid fighting, and the second will scare the fuck out of you to ensure that you think of NOT fighting before you get your brass balls all up in a tizzy.