Here are some tips on how to paint interiors:

1. To avoid lap marks, roll the full height of the wall and keep a wet edge.

2. Mix several cans of paint in a large bucket for a consistent color throughout the room.

3. Let the paint dry, then cut the tape loose for a perfect edge.

4. Paint the trim first, then the ceiling and walls 1.

You can also check out this video tutorial on how to paint a room 2.

I hope this helps!