A most common of projects, painting is probably the easiest to do yourself but has a lot of pitfalls as well that you need to be aware of.
First you must decide on the type of paint. There are flats, semi-glosses, and glossys that you will need to choose from. The decision should be at least partly based on what is on your walls now. There are ways to test this we will discuss later.
Then you need to choose colors and the quality of the paint. Once that has been decided you need to determine how much paint you need. You can measure the rooms you plan to paint to get a good idea of this.
The cost of the paint will vary based on the quality. Keep in mind you also need trim paint. Additionally you will need drop cloths, brushes and rollers, extendable handles, wet rags, containers for the paint while you are putting it on, painters tape to tape the things you do not want painted before you start each section, and a screwdriver to remove fixtures and wallplates before you start the job.
A site that goes into very deep detail on all of this is Painters Richmond Va located in Richmond Va. You will come away knowing all you need to know by reviewing this site.