A simple thought or add to any BOB: all important documents or copies thereof along with some cash. Documents such as insurance paperwork, social security cards, color copies of driver's license, shot records, Concealed Carry license/permit, account numbers with phone numbers, mortgage paperwork, titles, etc. (Need to be able to prove identity, that you do have a valid insurance policy, etc.) Some cash because cash is always good (whereas a credit card/atm card usually requires electricity and a working computer network). Recommend putting these things together now if you don't have them and have these ready for anything (including: wake up in the middle of the night and your residence is on fire and you have to get out NOW). Might want to put these in a "mini-BOB"...such as a fanny pack that can quickly and easily be added to/thrown into/stuffed into a "regular BOB." Fanny pack can also hold a hand gun so if this is all you have time to grab you still retain a means to defend yourself.
I think in terms of layering prepartions. And organized "mini-BOB." Working up from there to: A full BOB. Backup BOB (or vehicle BOB perhaps...more BOBs are welcome here...but not BILLs..
). Residence prep for what many call "bugging in" (though the term I grew up with was "castle"). Vehicle prep. Evac. plans (mulitple routes to designated destinations). Etc.