grades

Any of them. Every house has the potential to take a grade risk if they like you enough. Every house has the potential to make an exception. The lower tier houses are much more likely to take grade risks however. (Except for Chi O)

Get recs, have a killer resume, make connections, and be prepared to put your best foot forward.

Don't try to plan out which houses you have a best shot in. I ended up in the last house I would have imagined I would have ended up in based on the research I did the summer before. I know it's hard to be patient, but just wait until recruitment and see what happens. None of us can tell you where you'll end up.