If this is a specialist, make sure you have obtained the proper referrals from your primary care doctor
Call the specialist as soon as you have the referral in your hand to see what their process is for new patients. Some specialists need a lot of paperwork, records, and will not see you (even if you have a PPO) without a letter and formal referral from the referring physician.
If appointments are being scheduled months out for new patients, ask to be put on the cancellation list.
Do you have a detailed health profile? If not, this would be a great time to make one, be sure to include basic information, risk factors, current issues, past surgeries, any medication you are on, (include herbs and vitamins), family history allergies etc.
Get copies of your health records and any imaging.
If you have had an MRI, CT Scan, or xrays done, get copies sent over to the new doctor. This will give him time to read them in advance.