Well, ideally I would like to always be in the 10-12% range, but when gaining, it's hard to do. To get there the first time around I did a diet with a coach named Dave Bair. It was a straight-up carb cycling diet with 5/3/1 as my weight training and treadmill in the morning. The diet progressed over a 12 week period and at the end I was lean as hell, probably 7-8% if I had to guess.
My mistake was that I tried to gain too quickly afterwards and put on too much fat. Now I am leaning out again in an effort to gain the right way, slowly.
My approach this time is a little different. I started by finding my approximate equilibrium carb level, meaning if I eat carbs with just about every meal (less in the morning, the bulk after training), does my weight stay about the same. Once I found this, I cut out the bullshit foods, which for me was any kind of dairy and "fat" foods like nuts, avocados, and olives. Those foods aren't bad, I just had plenty of fats from steak, eggs, and dark meat chicken to support my body. The added fats were keeping me fat. I also began doing the prowler 3 times a week for conditioning.
The next step was to begin to eliminate carbs from the meals furthest from my training time. This was a John Meadows recommendation. Over 2-3 weeks I took them out of the first two meals of the day. This is where I am currently. Read Meadows' articles and sign up for his website for a couple of months. You will learn a lot from him that you can actually apply to yourself easily.
Next, I will cut down on the amount of carbs in my off days, followed by conditioning on my off days.
The key to this is to add activity and/or take away carbs to progress the fat loss. If you want to really do this, don't fuck around. Hit the fat loss hard as hell for 8-12 weeks, and then add carbs and overall calories back slowly so you don't negate all of your hard work. Only use junk food if you have to. This was my main problem. I would pound the milk, PB&Js, and cheeseburgers because I thought it was hard core weight gaining. Nope, it was my inner fatty dictating my eating habits like the fat little turd he is. I should have kept one prowler day in there a week, and eaten cleaner on the way back up. The foods you eat while dieting are the same you eat while gaining, just in different proportions.
Jim thinks dieting is gay, and it is. But, I hate looking sloppy and I don't mind saying that. So, when I get sloppier than I want to be, I diet for a while, with focus, and then get right back to what's important, getting stronger. Also, when you're leaner, you don't gain as much fat when you are trying to put on muscle.
Ok, enough diet gayness, now let's all go listen to Dragged Into Sunlight.