There are several ways to evaluate a management company.
1) Consider where the company is located and how long have they been in the timeshare industry?
2) Find out how many resorts they manage.
3) Check out the quality of those resorts, and find out about maintenance fees?
When you're ready to show your timeshare, will the management company assist you or your agent in showing? Bear in mind that once you're with a management company, if you are not satisfied, when the contract expires you have the option of finding a new one.