Our MS IT group pulled together some "best practice" guidelines for building applications against TFS.  We did this because we've started to see people build some internally that put a lot more load on the server than they really should.  They just sent me a final draft to review and it looks pretty good, so I thought I'd share it.  It doesn't cover everything one could imagine but it's some good tips based on our (the TFS team's) experience building tools.  I've attached it to this post.