Driftwood's supposed to have been tossed around long enough that it's actually dead (so hopefully less likely to leach out sap etc.) and also somewhat preserved so it's less likely to rot in your tank.
The pieces I did, I scrubbed and boiled, then soaked with a weight to hold them down. Took about a week or two until they actually sunk. (Of course I then decided I didn't like the look as much and didn't use them)
The big things with found driftwood are sterilizing (boiling is probably safer...having it catch fire while you're trying to bake it wouldn't be fun) and for some people, removing the tannins (what turns your water yellow). That part you don't actually have to do if you're impatient and don't mind your water being discolored.