How can I help my child deal with pain at the doctor's?

Depends on age. Infant or small child, just hold and comfort. Older child discuss just before it happens, be calm and reassuring yourself, tell them will just take a second (if a shot) and give them something to look forward to afterwards such as lunch out with you etc. If severe pain, ie wounds, fractures etc get pain medication from your physician and administer according to directions.