I've posted ads on Craigslist before. Ask for references, make sure they went to a farrier school (it definitely helps narrow down the pool of people all vying for your money and saying, "I trimmed a horse once!"), see pictures of their work, etc. Ask to see pictures of their horses feet if they don't have any current work pics. Then work out a way to meet them halfway or something. Unfortunately we have to deal with the exact same thing. Hardly any farriers, all of them self-taught. Not that being self-taught is bad, but you can tell the difference between one that's worked at it, and one that went out, bought the tools, and started trimming with no experience or guidance.
If you're looking for books on self-trimming, or just want to see what a good trim should look like, you should check out Pete Ramsey. His website is: Pete Ramey Hoof Rehab home. Horse hoof maintenance and care.
The man is amazing with hooves.