The National Blood Authority has been working on some excellent, evidence based guidelines to help with all things transfusion in a few different settings. Three out of six are complete, with the remainder due in 2013. They are well written and comprehensive, and break down a lot of the myth and dogma surrounding transfusion.
They have been kind enough to provide the guidelines free of charge, in full and as handy quick reference guides. You can even order a free hard copy if you live in the pre-digital world.