Different riders have their own preferred cadence (speed of pedalling) for climbing. Generally, a faster cadence, in a lower gear, is regarded as the most efficient, as you aren’t forcing your muscles into fatigue.

Fitness: How cycling affects your hamstrings

On a shallow hill, try to stick to a cadence about 80rpm, dropping the gears so you can maintain this comfortably. If it’s steeper, you are probably going to have to slow the cadence down, but try not to ‘stomp’ a high resistance unless there is no choice.