The one meal a day is a common mistake. Let's start with the basics of dieting. Everyone is built differently, and everyone want different things for their body. Are you just loosing to loose weight, or also get toned, get more energy, have higher stamina, etc. etc. All these things matter. No matter what you're looking for though there are some overall pointers.
4-6 meals a day, and a snack counts as a meal even if it's just a handful of peanuts and dried fruit. When we define a meal, it does not require to be extremely filling, moderate your portions, do not over eat in any of them. This is how we keep a high metabolism. Also, use smaller plates. Smaller plates and bowls make a meal seem like more than it is, and helps you adjust portion sizes without making your mind feel like you're not eating as much as you'd like.
As far as what to eat. Try to cook your own food as much as possible. Most food bought or instant are extremely high in sodium, which is a dieting sense is even worse than fats and sugars, although you'll have to watch for those too. Sodium interferes with the amount of water and protein you're working into your system. Eat complex carbs, whole wheat and brown rice that kind of stuff, and lean meats. Chicken breast meat are the favorite of those trying to get lean and toned. Fish, especially salmon is high is good fats like Omega-3 which is important to the diet. If you like fresh fruit, try not to have it as an after dinner snack, it has more sugar than one thinks. Drink lots of water, and cut down on alcohol (this on is always hard for me, I loves me some empty calories).
Lastly, try to get some regular form of exercise. People often make the mistake to think that walking for an hour in adequate. Walking is good, but you need to actually raise your heart rate and seat for a certain amount of time before you're burning any fat. Different exercises target different areas of the body, so try to do a variety of things, plus it keeps it from getting too boring. Try to get an buddy to work out with, and commit to it.
Finally, if you mess up along the way, don't give up! Too often people will give into a craving, have a midnight snack, eat at a fast food restaurant and give up because the diet is ruined. Let yourself break the rules once in a while and be a little bad and you're far more likely to stick with it until you've reached your goal.
Hope some of this helps and best of luck. If you want some specific pointers feel free to ask.
