Anything. I work with a very large multi-specialty clinic with three quarters of the docs internists and primary care. Many of them wear jeans and flannel shirts. Some wear khakis, blue/white shirts and a tie.
They will not care what you are wearing, as long as you are fully clothed.
Keep in mind that many PCP referrals are garbage, relative to referrals from neurosurgeons/orthopods. Be very clear about the type of patients you feel you can help that would be worth seeing. Not everyone thinks the way a pain guy does and they need some guidance to what is a good referral and what is not.
If you are a low cost provider, point out the advantages of your practice over others in reducing the cost of procedures and imaging, such that their ACO contracts could benefit from your services. Particularly, tell them you do not require imaging for an "admission ticket" (high cost and wasteful) and that you will decide who needs imaging and who does not. Many practices REQUIRE imaging before they see patients, which is medically absurd and wasteful.
Emphasize that you are nice to patients. Too many pain/spine docs are complete asses to patients. This information is returned to the PCPs and they are not very happy about such treatment. Keep in mind that it takes more work to be a jerk, so just realize that your patients have better things to do with their time than being told they are fat or lazy. Everyone who is fat and lazy already knows that and they don't need to be insulted when they are paying for the time.
Bring some treats, like cookies or a few cheesecakes, bring some info, and make sure you leave a bunch of cards with the SCHEDULER. The scheduler and nurses are more important than the docs, as they decide where the referrals go.
