You haven't said whether this is house painting or artistic painting, but I am going to assume it is the former. Remember, paint drips, no matter how carefully you paint. So, anything that you do not want to get paint on, should be covered (e.g., the floor). You can cover things with newspaper; it's cheap and you can throw it out afterwards. And wear clothing that you would not mind ruining with paint. People who paint with any frequency have special clothing that they wear only when painting.
Different kinds of paint are made for different purposes. There are indoor latex and outdoor enamel paints. Use the right paint for what you are painting. And also bear in mind, a latex paint cannot be painted on top of an enamel paint, it won't stick properly.
Surfaces should be clean and dry before you paint them. Do not paint over old, peeling paint, you have to scrape it off first, because if you don't, the new paint will just peel off with the old paint underneath it.
The color of your walls should be compatible with the color of your furniture and/or carpet. For that matter, bland, neutral colors are often a good choice for walls because they go with everything. White makes a room brighter; if the lighting in the room is not that good, white paint will help. Do not paint a wall black unless you are suicidally depressed.