Staircases have to be used on a regular basis, so you will need to plan ahead when painting them so that they can remain functional while new paint dries. The simplest way to tackle painting a staircase is to paint the balustrade (handrail) first.
Make sure that you avoid drips and dribbles of paint as you work, especially where your brush touches the edges or moldings. Then move to the top of the stairs and paint the treads (the part you step on) and risers (the upright back of the tread). If you cannot take your staircase out of commission for long enough for the paint to dry, then on one day paint all the risers but only every other tread.
Cut some pieces of paper or stick ‘post-it’ notes onto the unpainted treads so that users know which treads they can walk on. The next day, paint the remaining treads, clearly marking where feet can be placed. Next paint the balusters, the newel posts and string. Make sure you have enough light and that you can reach the upper, exterior parts of the balusters safely. Intricately molded balusters and newel posts can be tricky to paint, so to avoid touching and smearing new paint, paint every alternate baluster and let them dry.
Remember to keep rooms well ventilated when painting and avoid naked flames. If you are asthmatic, it would be advisable to wear a paint respirator.