SA Group Allocation NYC

I've read a lot about different group preferences etc. but I'm curious to know how often do people get placed in the group they want to be in?

Are there any firms (GS/JPM/MS) who don't even care what your preference are and would place you wherever they seem fit? Or is there a way - aggressive networking/more introductions to team/VP connection - to get into the group you want to?

And would have a related major or previous internship help to get the group you want? Oil/Mining related internship to get Nat Res or a healthcare related major to get healthcare group?

Thanks for the help!