I found a neat blog about best practises for orchestrations in BTS.

Another great addition to this blog can be found here. This is a check list to review BizTalk code.

A third great blog has some tips and tricks on how to program BizTalk code.

Links:
BizTalk Server 2010 – Orchestration Best Practices – TechNet Wiki
My BizTalk Code Review Checklist – Richard Seroter’s Architecture Musings
8 Tips And Tricks For Better BizTalk Programming – MSDN Magazine