It's important to think what colors you would like. I stick with light neutral colors. You can't go wrong with that. If you want to paint a room a particular color, have a focus color, like a piece of furniture in the room which echos that color.
I painted my living room a very pale green, very pretty. At the same time, I purchased a new sofa, also green and I put up green vertical blinds (different shades). These shades are complimentary, but not matching. And don't match the carpet with it! That's just too much. My carpet is a neutral beige.
I did the trim for the entire small condo in a slightly darker shade of pale green. So I had the bedrooms to do. I didn't want them green as well, but wanted to use the green trim color throughout the condo. I chose an elegant very pale silver color, nearly white, but with nuances of green and blue, which goes great with the pale green trim color. I had large white fan installed in the master bedroom and this goes well with the walls. I love white in bedrooms and have several white whicker pieces. Later on I bought darker grey vertical blinds for the bedrooms. They compliment the pale silver of the walls.
Before painting you might want to do some dry wall repairs to the walls. I hired someone for that, as I was putting in ceiling fans anyway, and needed dry wall repairs. You can do this yourself, just spackle and small holes where nails may have been and take care to smooth out the imperfections.
Tape around your baseboards well. If you do the painting yourself, really take the time to do the prep. Buy a canvas drop cloth to cover the floor. Move the furtniture out of the way. Do small amounts at a time and don't rush your job. After it dries you may need to apply another coat, depending on how "thirsty" your walls are, and what color was underneath. Lightly sand your woodwork before applying the paint to the trim.
here's my living room:
Another thing: when you pick out the colors find a "set of colors" that go together. Usually they are grouped together. That's how I matched my flat paint with the trim in the living room.