In my personal experience your 'diet' (eating habits) is the key to weight loss and maintenance. Exercise is important of course, but it's very difficult to 'out-exercise' a bad diet. (http://www.workoutstrength.com/blog/weight-loss-is-diet-or-exercise-more-important/ )
I hear it time and time again, people talking about how much they work out and yet they don't really ever lose weight. Then I ask and find out that they haven't really changed their eating habits, or they have been mislead by food marketing into thinking they're eating healthy. I'm not a nutrition expert, but I do know what has worked for me personally so I thought I'd share :)
Easy on the 'Variety':
I usually eat 1-2 meals a day that are always the same. When it comes to meal planning and eating habits, 'variety' can be a danger. A lot of athletes use the same idea with having the habit of 'routine meals' that they eat everyday. It also makes meal planning a lot easier because you already know what you're going to eat :)
I typically always eat eggs and toast every day for breakfast. (1 whole egg, with 2-3 egg whites (from a carton of egg whites), with a non fat cheese slice on top and one slice of whole wheat toast with margarine). It's a no brainer. That's just what I always eat.
If I'm working I always pack a salad with some element of protein for a 'meal' (I'm a nurse and it's always random shifts so sometimes my 'lunch' is my 'dinner', so I'll call it a 'meal'). I change up the salads a bit: some days it's a Greek Salad, or greens with walnuts and cheddar cheese, sometimes Caesar... unless I've run out of lettuce, I always pack a salad. It's become my routine. And I NEVER order out at work or BUY food from the cafeteria. Take out meals and Cafeteria food are almost always very unhealthy and Expensive! (This is another point that I think people get wrong: Eating healthy is actually more cost efficient. I have a 'cheat day' every week usually where my fiance and I buy junk food and have a gorge fest... it's pretty awesome... but it usually costs a small fortune to do it. Our regular 'healthy' diet is much more cost efficient.)
For snacks during the day I have apples, low fat yogurt, crackers with low fat cheese and pickles (smoked oysters too when I'm feeling extra fancy), microwave popcorn, or toast/rice cake with peanut butter. My fiance made some protein/banana muffins so today I'm having one of those.
Dinner meals are normally the meals that have a bit of variety all depending on what ingredients are in the house or what we feel like eating. Sometimes It'll be whole wheat spaghetti with lean ground beef, or roasted chicken with veggies, jasmine rice or potatoes, sometimes I'll have another salad for dinner, or thin crust frozen pizza. (The 'protein' element in your meals doesn't always have to be meat. You can get a 'complete protein' from eating grains with legumes. So sometimes I'll make a pot of rice and then put a can of legumes or beans into it and voila!!! a complete protein.)
I've recently started to steer away from eating 'animal products'. There is a lot of research out there indicating the vast benefits (not only to the individual put to the planet) of an 'animal free' diet. I'm no where near a Vegan or Vegetarian but I do try to minimize my animal consumption. In the past year I've switched completely over to Soy Milk instead of Cow's milk (see the documentary 'Forks over Knives' for more convincing info).
Grocery Shopping Tips:
When it comes to grocery shopping I usually try to stick to the 'outside parimeters' of the store. It's those inside aisles that can be super sneaky, and tempting with its deliciously, fattening, sugary foods. The outsides of the grocery store have the fruit/vegetable section, the bakery (careful there though!), the meat section, Dairy, and the Frozen Foods section. I buy a lot of frozen veggies and add them to rice dishes, pasta, or just warmed up with a little margarine and salt and pepper (I sometimes eat that as a little snack). I do venture into the 'middle' aisles of the store for canned lentils, beans, salsa, condiments, salad dressings, olive/canola oil, soda crackers, and microwave popcorn. I also make it a habit to never buy cookies, chips, granola bars, side kicks or prepackaged instant 'rice meals', or any dessert items. My dessert of choice is a glass of Red Wine! :)
Cheat Day!! :
If we are having a cheat day, which is usually once a week or once every two weeks, we will buy chips, cookies, nachos, McDonalds or any junk food we want, but only for that one day. I usually try to keep it to one big 'Cheat Meal'. But just for that day. The junk food is not to be hanging around the house all week. My will power couldn't handle that kind of temptation around all the time. The way I am is, "If it's in the house, I'll eat it!". I don't lie to myself about my will power level because I know it sucks! You have to make your home a 'safe area' for your diet and health. I don't have junk food in the house because around 9pm at night I'm bored, and I'm stressed.. and I just want to binge! lol
Anyways, I'll leave it at that for now. I'm not saying that my way is the best way, or the right way, but for the most part it works for me. The only exercise I've been doing regularly for the past few years is walking my dogs everyday. I attribute being able to maintain a healthy weight to this method of eating (although one of my personal goals for this year is to start exercising more).
Best of luck!