There's 'best for BIF' in which case Geoff's advised list is good and there's 'possible for BIF' in which case you can get away with pretty much anything - I initially used an M42 400mm telephoto, so requiring manual everything - which massively helped my DIFs (Dragonflies in Flight) but I've used 70-300 slow lenses as well as 100mm. Whatever you use, three things are pretty much vital: practice, practice and practice!
