There are some extremely insightful posts here. The only thing I'll add is: OOC communication can be important. For some, it needs to be consistent in order to establish that sense of trust. It might not even take that long; with my RP partner, all it took was a few days of OOC and IC conversation for me to enter my comfort zone. Your mileage may vary, but my advice is to not be afraid to approach OOC where warranted.
