Look for a local firm that has an office overseas. Then, the local lawyer will be ultimately responsible for the work done there and you have recourse in case something goes wrong. Big law is pretty much fungible these days, there is really very little difference between one firm and another. If you have a contentious matter, it's a little bit different, but if you can you should try international arbitration rather than use the legal system of either country.

It's really tough if you aren't one (probably akin to the often-mentioned difficulty non-technical folks have evaluating programmers).

But there are a few places to start. First, Martindale-Hubbell is a respected reviewer of legal talent and provides ratings.

Second, if your lawyer happens to be a "SuperLawyer" you're probably in good hands. SuperLawyers represent the top 5% of a given field as voted by their peers.

Hope that gets you started.

If it's a US or Canadian lawyer try searching for their name on http://www.talkburst.com/ - anyone with a name can be reviewed now.