You can boil smaller pieces, larger pieces I usually soak in a big rubbermaid trough, or weight down with rocks I work into the aquascape. Anymore, I usally try to buy african or malaysian hardwoods, as they sink without any help.
with the size tanks people on this site generally have, and the size driftwood that looks good in there, boiling is not an option. Except for if you work in a big cafereria and use the 200 gal soup pot after hours Anyhow, I tied my driftwood down with fishing rope, onto the big rocks underneath. That works quite well, and after a few weeks you'll be able to test on the tension of the line if you need to give it some more time. This is much safer than putting rocks on top, which could fall down into the glass or the wood pops up thru your top cover when the rocks fall off.
Have fun, driftwood is a great decoration. I harvested my own driftwood, it took me a solid hour of sawing to get it out of the middle of a stream. Always bring a saw when you go canoeing
I won't go in to sanitizing since you didn't ask (but bleach and water left for a while works if you can't "boil it"). I usually sink it with rocks until it no longer floats. I've had some sitting so long they grew algea which made it more realistic.