You see it all the time. It is asked "what's your diet like?" and the reply is "don't worry about that, the diet is good, my problem is somewhere else..." OK, fine. Sure, we all eat somewhat regularly and try to get a good amount of protein. But is that enough to call what you are doing a "good diet"? Not by a mile.
Here's a few things that help knowing where you stand with your diet:
1. Know how many calories you need for maintenance on both active days and rest days.
2. Know how many calories you are taking in each day. This means keeping a food journal. Unless you have kept food journals for a LONG time, then you can't really know where you stand with regards to your nutrition. A good place to keep a food journal is at FitDay, which also calculates how many calories you need. It's free, too. Here's the link: http://www.fitday.com
3. Know how much protein you need and how much you are taking in. Protein is the single most important nutrient to watch, at least in the early stages of discovering your best diet. 1g/lb of bodyweight is a good base, which means that under no circumstances should you go under that. 1.5g/lb of bodyweight is good and some people do even better at 2g/lb.
4. Know that there is protein in many things. "protein" doesn't mean "powder". Fish, chicken, meat and dairy are all high in protein.
5. You need to know which nutrient ratios you do better with. If 40% protein, 40% carbs and 20% fat works for you, you HAVE TO KNOW THAT. If 50/40/10 is better, then fine. And so on. Some people do very well on 40/05/55 for 5-6 days, followed by 40/50/10 for 1-2 days. That's called a CKD.
6. To discover these things, you will need to experiment. Start with a good 40/40/20 and see how you feel. Adjust and see the results. Then again. Then again. You'll eventually find what works best when cutting, when bulking and when maintaining.
7. You need to eat REGULARLY. That doesn't mean "every single day". It means every set number of hours. For example, say you're up 16 hours per day, and sleep for 8 hours, then you can eat approximately every 4 hours. You can schedule things like this:
03PM: Pre-workout Snack
06PM: Post-workout shake
1000: Bedtime snack
Yes, this way you eat 7 times a day. This is pretty ideal. Too much work? No time? Too much trouble? Then either hire someone to do it for you if you have the money or get it out of your head that you will ever have anything more than a "nice" body. Being in GREAT SHAPE is a lot of work! If it were that easy, you'd see legions of 235lb men with shredded 6-packs. THAT is why there aren't that many. Yes you can get away with eating 4 times a day, but 5 to 7 are better.
8. Know what you're doing with what kinds of carbs, fats and proteins you're taking. Know what low glycemic index carbs are, what high-GI carbs are and which do what for you. Know what essential fatty acids are, what saturated and unsaturated fats are, which foods they come from, what they do for you. Know what complete protein is and what isn't and make sure you have complete protein on as many snacks and meals as doable.
9. Once you've been at training and dieting for long enough that you have experimented with enough variations of all these factors and finally figured out what works best for gaining, leaning, or maintaining/recomping, and have disciplined yourself enough to apply all this knowledge no matter what, day in, day out, THEN you can say you have a "good diet". Not before.
Remember, a chain is only as strong as its weakest link. This is true of bodybuilding also. If you think of Training, Diet, Supplementation, Rest, Hydration, Hormones and Genetics as the links of the chain that ties you to your bodybuilding goals, then you have a pretty good mental picture of how things work. In this author's 15 years of bodybuilding experimentation and 11 years of internet discussion of bodybuilding, DIET comes on top as the most often weakest link in someone's approach to bodybuilding. No matter how much stronger you make the other links, if diet is not as good as it can be, all your efforts to make those links stronger will come to naught because your diet breaks your tie to the "building" part of bodybuilding.
How many times have I met people in my gyms who complain that "gaining muscle is SO hard" and even that they are "steroid non-responders" or, the newly best-loved method of bull****ting oneself about their way of doing things, that they "have bad genetics". As a matter of fact, unless you have tried every single combination of every factor that is known to affect the bodybuilding endeavour, or have undergone a nonexistent DNA test to this effect, you cannot have any idea if you have "good genetics for bodybuilding" or not. Sure, your dad and grandad might be weaklings. Maybe their lifestyles made them that way and they just wasted great athletic genes by being potato couches or whatever. Point is, what your immediate ancestors look like doesn't mean much. Every single time I've chatted up some guy who complained of his gains or genetics or lack thereof, there is a gaping hole in his method, and most of the time, it boils down to ONE THING. DIET