I went to my local hospital with a list of approved providers and asked nurses at the nursing station who they would recommend for their elderly parents. I found a good gerontologist and then he recommended all of the other types of physicians (cardiologist, orthopod, etc.). They may be reluctant at first, but once one started talking to me, I got lots of good info. The other suggestions are also good!
To find doctors that are highly rated, check out the website healthgrades. Also, check with seniors in the community, church, wherever you may meet and talk to them and ask.
Like Pam said above, get a list of providers from your Dad's health insurance provider.... then go on the Internet and research out each and every one... look at their resumes, location of office [you don't want to be across town because one's parents tend to go to the doctors' offices quite a bit, closer the better]... then make an appointment to introduce yourself and your Dad.... if the office is bright and cheery, the Staff is all smiles, and the doctor knows what he/she is talking about and has a good bedside manner, then you have a winner :)