- what country you're talking about
- where you were educated, more so residency but med school can be an issue
- what your specialty is and what certifications you have
- what citizenship(s) you (or possibly your spouse) hold
- what languages you speak and how fluently you speak them
- whether you want to work permanently, locum tenens, etc.
- whether you want to work in a big fancy hospital or if you're willing to go where the work is needed
- and on and on and on...
I've read on SDN that while the MD is well accepted in most places, countries with nationalized systems are iffy with foreign doctors. Correct me if I'm wrong but you have to pass a series of tests including being fluent in French to practice and get reimbursed by the government in France.