Small cheap humidifier (like the type your mom used to use when you were sick as a kid - but without the menthol!) is good for adding moisture which helps "settle" the dust. Ctein uses black plastic stapled to walls in his darkroom and wipes them down with damp cloth occasionally.
I used to use the Black plastic trick. Charge it up with static electricity and the dust is attracted and held there instead of your negs. Since it's Black, it is easy to see when it gets too dusty and time to wipe it down with a damp cloth before recharging it.
I have a different theory... the only time I worry about dust is just prior to putting a neg in the carrier! Regardless of how careful and clean you are you still need to clean the neg before making a print.
I do vacuum the floor occasionly (with vacuum system that's located in the garage and runs thru the house walls.. can't think of what their called at the moment... so it doesn't expell dust filled air back into the same room!) and wipe the benches every now and then. When I get the urge for a bigger clean up and move the enlarger, paper safe and bits 'n 'pieces lying around, they usually have heaps of dust under them.
I am looking at installing a simple positive pressure system in my darkroom (shortly to be built). You use a fan to force filtered air in (you can use foam filters from a car accesories store I am told) which forces regular air changes. Not only does it keep dust down, it controls humidity and gets rid of those chemical orders when tyou aren't about...
I'm so frustrated with dust that I'm having custom glassless carriers made for my durst l184 enlarger. The 4x5 and 5x7 carriers are designed to work with and without glass. The 8x10 will only use one piece of glass. It never fails that I get a piece of glass or two between the negative and the glass. Arrrrgghh.