How would you do this for an acoustic?

You haven't made it anywhere until they make an action figure of you.
well, you'll have to do this whilst changing your strings, cos they kinda get in the way
when there's no strings on your acoustic, look through the hole thing (i never learned what it was called) and find where the neck connects to the rest of the guitar
now at this point there should be a little metal ring there with a hole shaped like a hexagon. get some sort of screw driver, stick it in the ring thingy and turn it
one way raises the action, the other lowers it
Quotes from other UGers in your signatures that talk about how good you are suck donkey schlong.
pretty sure you can chizel or sand or something down the nut, to get lower action on the lower frets.
Yea, and I'm "pretty sure" both of the above replies are junk.
leafy, don't bother posting again if that's all the better you can do, cuz that answer is as wrong as it get's and if someone were to actually take your advice(if you can call it that) they'd wind up with a screwed up guitar.
Hetha, it doesn't sound like you know what your talking about either, so plz just don't.

To lower action on an acoustic, remove the saddle and sand the flat bottom side of it down little by little until the strings are where you like them to be as measured at the 12th fret.
If you want to lower it by 1/32 of an inch at the 12th, then you need to remove 1/16 of an inch from the saddle.
To lower action up at the headstock end of the neck, either remove and sand down the nut, or file the nut slots deeper. Filing deeper is not recommended for just anyone because they need to be the right shape and size for the strings.

edit: dang, beat to the punch by tom.
another way that's fun is to buy a cheap saddle for a buck or two at the guitar store and file the crap out of it to reduce your string height to as low as it can be and then a bit lower as you learn how changing the action changes the way it plays and buzzes, and then when you screw up that saddle by sanding (files are faster) it too far start over with another one until you find the string height that is just what you want.

Then take that saddle and make a replica out of a bone saddle ($10) and then you are all set!

Plus you learn a lot.
Oh, and just loosen your strings so much that you can get the saddle out between sandings, without removing the strings. Then pop the saddle back in, tighten the strings and get playing.

Repeat until you are happy.

Then get some new strings too!