Having more intake fans than exhaust fans will makes it so that the case will naturally want to "exhale" air out of all the vents. This way you can make sure that air only enters through the fans and hopefully, through a filter. Keeping the case off of carpet and away from pets and smoke will also help a lot.
Also, not having your case fans cranked all the way up will help too. I think that's a big reason why my case stays relatively low on dust. If you just plug your fans in to the PSU it's going to have them cranked, but hooked up to a controller and dialed down they'll still move some air but with less resulting dust.