Give this a read: Disaster Recovery Guide
1) You don't need to stop any services
2) Backup your SQL Database daily
3) Backup your Exchange environment daily
4) Backup BES Server System State daily
5) Backup "C:\Program Files\Research In Motion\" and "C:\Program Files\Common Files\Research In Motion" directories daily ... you can really get away with not backing this up daily and just do it weekly if you don't have any custom software configurations or don't care about not backing up your logs all the time (but I care about my logs a lot; so I back it up daily).
Push comes to shove though, in a DR situation, you don't need anything on the BES to get basic functionality back ... you just need Exchange, the DB, and the installation software.