Depends on the type of pimple...
There is little you can do if you are going through hormonal changes which cause pimples... This happens at puberty or if you are altering your hormones through supplements.
First try the simplest solution. Wash your face several times per day with warm water and handsoap (old trick) :) This helps to dry out the skin and dry up the pimples.
Pimples may also be a reaction to your food. Eat clean for 1 week and see how things go. Cut out dairy, fried foods, wheat, grains, and foods high in saturated fats (red meat), caffeine and alcohol. Instead, reach for fruits, berries, almonds, greens, cauliflower, peppers, fish, poultry and eggs. Cook with olive, avocado or coconut oils. Finally, drink a herbal tea like rooibas or green tea. This diet is high in healthy proteins, fats and really big on anti-oxidants, which cause all sorts of unpleasant reactions by the body, including pimples as the body tries to get rid of toxins.