To gain weight, you need to be in a calorie surplus of your BMR. In general the 250-500 calorie range is best per day.

To maintain weight, you should eat very near the exact number of calories you burn each day. A little bit over or under will not make a big difference.

To get lean and/or lose body fat, you need to be in a calorie deficit.  In general the 250-500 calorie range is best per day, while your diet should be low in CARBS, high in PROTEIN.

These are all approximates. They may need to be adjusted depending on the individual. Play around with your own macros and total calories until you find the method which gets you results.

Related Questions:

1. What is my BMR, and why is it useful?
2. Are carbs really bad?
3. How much protein should I eat to gain muscle? How much protein is too much?