From a docs perspective this is the thought process that goes through my mind when I'm making a referral.
#1 - asuming that all the specialists have EQUAL clinical skills for the referring procedure (sometimes that can be a big asumption to make though), one of the 1st things I consider is the personality of both the patient and the specialist. Lets be honest, some Docs have more laid-back, "nicer" chairside manners than others, and if possible I'd rather not send a say "nervous" patient to a specialist who usually has less patience, and vice versa. Also, I always ask myself before handing the referral slip, would I want to go see that specialist for that procedure if I needed it myself? If I wouldn't want that doc to do that procedure to me if I needed it, then why would I want my patients to see that doc for that procedure??
#2 - geography. If I as the refferring doc have the ability to send a patient to a specialist of equal ability/chairside manor whose office is say 5 miles from there home vs. say 20 miles from their home, well more often than not I'm referring them to the specialist that's 5 miles from their home
#3 - Insurance plans (a small consideration on my part) Especially if it's a medicaid patient I'm referring out to a specialist, not all specialists will take medicaid, so in that scenario that often influences where I'd make the referral
What I DON'T consider when making a referral
1) What did that specialist give me as a Christmas present last year/how many times has he/she taken me out to lunch/dinner recently
2) Cost (medicare patients excluded). I'm going to make my referrals on the basis of skill of the provider and personality of the provider