I'm currently doing some physics research at a university, and take an ethics/preparation class for grad school... and this question came up. We were told to ALWAYS approach the professor in person if possible. secondly, if they are a professor you are skeptical about, use this approach. Walk up to them, look them straight in the eyes and ask them "I'm applying to these law schools____ would you be willing to write me a GOOD letter of recomendation?" watch very closely to their reaction... if they hesitate at all MOVE ON!!!! secondly, just a word of advice. If they ask for 3 lor , do 5. You never know when a professor will forget (they are lazy just like us) or submit past the deadline. Even if all 5 make it - having 5 lor wont hurt you... however only 2 when they asked for 3 DEFINETLY will.