I can't take credit for this idea (I read it somewhere at MDC) but we keep a little basket or box in the most-used rooms to put small objects that inevitablely end up on the floor (pennies, plastic tags from clothes, paper clips, large dust bunnies). The basket/box stays up on a shelf, and it just became habit to scan a room and throw anything in there that was chokable. I suppose you are supposed to empty the basket at some point. :LOL
Other than that, the usual cabinet locks except on cabinets that hold stuff ds can play with, lots of empty bottom (and 2nd, 3rd) shelves and drawers. We also just close the doors to rooms that are off-limits and it's almost time to invest in the doorknob covers and some sort of front stove guard since ds seems to get taller by the minute.
The Christmas tree was an interesting challenge...
good luck!
Heidi