Advice above is great; math is pretty much how I maintain my weight. However!! One addendum:
Originally Posted by sexytime10
TL;DR Weight loss is just math, hit your numbers correctly and you are guaranteed to lose or gain weight.
True 99% of the time.
-- and this isn't for the OP so much as anyone who might be thumbing through this -- if you are sticking to your outlined diet perfectly and still not gaining or losing weight, don't be afraid to check in with a doctor. My mom struggled with trying to shed extra pounds for many years despite maintaining a healthy diet, before finding out that she had severe hypothyroidism which was causing weight gain and water retention.
Moral of the story, pay attention to your body & don't get discouraged; everyone is a little bit different.
Personally, apps like MyFitnessPal have been most useful to me as diagnostic tools. I don't use it every day any more, but when I first installed it and kept daily logs, I noticed that I'd often hit my carbohydrate cap early without eating enough (or any!) servings of fruit or vegetables. I figured that since I was eating whole grains it wasn't a big deal, but in actuality I needed to curb my grain intake over-all in order to be eating a balanced diet. It's tough to notice things like that if you aren't writing down what you're eating.