It takes time for some people to start breaking out of their shell, so try not to get impatient if someone is still putting up walls. Do not try to force things -- you will only scare them away. The best strategy for getting someone more involved in the group or more involved with you is to give them time and give them space. Show them that they can be who they are and you are not going to judge them. Trust is all it takes to tear that wall down!