The UK's Society of Authors provides an excellent, free, contract checking service for its members, which is worth far more than the cost of a year's membership.

I'm pretty sure that in her book, From Pitch to Publication, the late and much missed Carole Blake talks about how she negotiated contracts for her clients, and the sorts of things she would look for, but I'm not sure. (It's a fascinating book about the publishing world: a bit out of date now--she was writing an updated version when she died--and well worth reading even if it doesn't have the information you need.)