Pick up a container of premixed drywall joint compound from your local hardware store or home improvement store. It's best to talk to the staff at the home improvement store and discuss the effects you want to create with the texture. They can help you determine how much joint compound you need to purchase.
Remove all the items from the room that you want to texture. Cover anything that can't be moved, such as heavy furniture, with a drop cloth to protect it. Place a drop cloth on the floor, too. Use a screwdriver to remove outlet covers.
Use a wide-blade taping knife to apply a thin coat of joint compound to the wall. If you want a rougher look, use your hand to spread the compound. Work in small sections at a time, starting at the top and working your way down.
Use different tools to create the texture that you want. Use items such as a stiff wire brush, paintbrush, comb or sponge to create swirls or designs on the wet compound. You could also use your fingers to make lines, loops or swirls. Don't worry about being perfect.
Alternate applying the joint compound and making designs in the texture until you achieve the look that you want.
Allow the joint compound to dry. Use 220-grit sandpaper to sand away any dry joint compound peaks that you don't like. Remove any sanding dust with a fiber towel. Reapply the texture as you desire.