Faux finishing is a painting technique used to create the illusion of texture on a wall.
It's developed into something of an art form, using simple tools like sponges and rags to produce effects that leave virtually no traces of the tools. But it is something that a do-it-yourselfer can tackle.
It's appropriate on drywall, plaster or wood, and it requires no more preparation than any other new paint job, just a clean, primed surface ready for finishing.
With most faux finishing, you're applying one or more accent colors over a base coat of your main color. The base coat is usually a regular latex wall paint with usually either a flat or an eggshell finish. The accent colors can either be latex or alkyd-based paints with the finish (flat or eggshell) matching the base coat. Latex paint dries more quickly which means you can apply another color much sooner, and it also cleans up much more easily.
But the longer drying times of the alkyd-based paints gives you more time to fine-tune them on the wall, and that can be a factor in getting the finish to look just right.
Applying Base Coat
The first step in any faux finish is to apply the base coat, and usually that's just cutting in and rolling out a single colored paint as you would on a normal paint job. Be sure it's thoroughly dry before moving on to the next steps.
Before applying a faux finish over your base coat, it's a good idea to test your colors and techniques on a sample board. The most realistic surface would be a piece of drywall, primed and then painted with your base coat. But cardboard or newspaper will suffice.
Whatever you use, practice the technique till you're comfortable with it and then move on to the wall. And if you're working with more than one accent color, working on a sample board will let you determine the best order for applying them and achieving the effect you want.