There's enough threads on here about building vacuum tables themselves. Not really explaining at all how I got mine built, but I've spent the last few days building a new base for the table and tweaking it to print quicker and more enjoyably.
I was printing flat before, I would definitely recommend angling yours if you haven't. I'm printing mostly with 36" screens, and my table angles from 36" to 48" high, I'm on the tall side though.
First and simplest improvement: Put a big light right above the table. People probably are smarter than I am and do this right away. For a while now I've been printing under bunk lighting and I'm happy I finally put in a 4x 48" fluorescent fixture above the table.
I put in a counterweight system, mostly inspired by the one done up by the guy that built his own one-arm. I used small aircraft cable and hung pulleys from the ceiling. I drilled holes through c-clamps to feed the wire. The pulleys are high up enough that the counterweight itself is simply two 36" lengths of 1" square steel tubing. I drilled holes through it so I could attach it to eye-bolts through which the cable could pass.
Lastly, I put a micro-switch in under one of the hinge-clamps. Combined with the counterweight, this has sped up my printing about 40-50 impressions per hour. Screen-up: vacuum off. Screen-down: vacuum on. No work necessary. When registering screens I just tape it down turn the whole system on.