Thoroughly clean and smooth a concrete floor before applying paint. Make sure no water is seeping into the concrete, and use appropriate painting materials. Begin by sweeping the concrete floor, then sponging or mopping with soap or degreasing solution. Allow the floor to dry completely, usually several days, before proceeding.
Sand down bumps and fill any cracks in order to create a smooth painting surface. Painter's tape is helpful for marking patterns or when using multiple colors.
After the surface is prepared, apply two coats of concrete bonding primer and stain blocker, drying in-between. Apply at least two coats of epoxy paint followed by at least two coats of acrylic-base masonry sealer. Allow time for drying between coats, and use proper protection when handling paints and chemicals.