phoenix has a great post, as i mentioned before the only thing i would ad is this:
1, besure they dont outsource your account it will be hard enough to deal with without having to track down your account make sure your account is with them and them only
2. how long they have been in business with proven track record. new companies havent established enough clients yet to know how well they work or they may be a former scammy place that changed thier name for a clear record.
3. besure they have good customer service who will be handling your account and how can i get in touch with them if i have a question
4. They should answer the tough questions honestly. most companies dont like to answer questions like can i get sued? but they should answer yes no matter if they beat around the bush. If they lie run. How will you ever be able to trust them with your accounts if they lie off the bat? ask them alot of questions that are tough for them to answer. Like can my creditors still call? (yes, although it should slow them down).
If you follow phoenix list, and these suggestions you should be on your way to finding a good company.
good luck!