Clean the surface with dish soap and water. Paint adheres better and provides more even coverage on a clean surface.
Brush primer onto the surface if you're dealing with an unpainted surface. A 2-inch synthetic-bristle paintbrush is ideal for most jobs. If the surface was previously painted, your new paint will be able to cover the old layers and priming isn't usually necessary; however, a light sanding is a good idea. Wait for the primer to dry before continuing.
If you had to prime the surface -- or if you just don't like the existing color of the chair -- paint the entire surface in the lighter of the two colors you want for your stripes. Use a high-gloss latex or oil-base paint and 2-inch foam paintbrush. High-gloss finishes are ideal for most furniture, because they are very durable and easy to clean. Let the paint dry thoroughly.
Plot your stripes using a tape measure, marking ideal stripe placement on the chair using a pencil. If it is too dark for pencil marks to show up, use a piece of white chalk.
Apply painter's masking tape to the edge of your pencil or chalk marks.
Using your second stripe color, paint the surface between the tape lines using a high-gloss latex or oil-base paint and 2-inch foam paintbrush. Wait for the paint to dry.
Apply a second coat of paint if needed. Wait for this coat to dry.
Remove the painter's tape after 24 hours. Avoid early tape removal, because this can lead to sloppier lines. Though the paint dries within hours, leave the tape on for an entire day. At this time, the tape will peel off smoothly, revealing crisp stripes.
Erase leftover or stray pencil marks, and wash off excess chalk.