During my residency many many years ago, the common procedure was to do lip reduction surgery, however, today people are opting for fuller more volume to their lips. Lip implants are still an option, however, I do not feel that they give the best results.
Silicone injections have been used in the past and they are extremely unpredictable. Today I almost exclusively use either Restylane or Juvederm to enhance the lips and perioral areas of the face. Typically it takes two sessions to complete a lip enhancement. Subtle changes are much better than dramatic changes. You will be asked to participate in your enhancement. I will make a suggestion, but you are ultimately responsible for what you want. Also, you must remember that I can only enhance what you already have.