Worms manage their numbers by the ammount of food they get. If you starve them, numbers go down, opposite happens when food is in abundance. Under optimal conditions there are 1000 worms pr. sq foot of surface are (IIRC)
At the moment i'm doing alternating sides in my bin. harvest from one side, feed to the other. I harvest around a half to a whole cup pr. day. When i reach the bottom, i put in fresh bedding and spent rootballs, add a little blended goods (things containing stuff the mj plants love - pumpkins seeds have high mag levels for instance) and then i move the top layer off the previous feeding side, to the new, and start harvesting from there instead. To lazy to do screening or dump 'n' sort.
I cut the stems of my mj plants into 1 inch pieces and add to the bin aswell to give the castings some structure - i plants in 100% VC atm, and it has a tendency to clump up and pretend it's concrete >.< I think of the stems as a VERY slow release nutrient (degrades slowly in pots due to microbial activity) and a structure agent.
When i feed i sprinkle a little sand in as well, to give the worms some grit (worms have gizzards), and over time the sand will be ground up and end up as minerals.
Eggshells are another good thing to add, since the worms use the calcium for reproduction and digestion (worm mucus is high in calcium bi-carbonate), and they add a nice ph buffer both in the bin and the end-product. Sterelize them by heating them for a while (also makes them more brittle and easier to crush) You can put them in a blender as well, but there are some precations. 1: dust - do not inhale. 2: if you add water, you don't get dust, but instead a complete mess. I blend it with some foodscraps and a little water untill everything has a consistency of toothpaste. Be careful with blended food, it can heat up and kill the little buggers.
On a final note (i think i can go on about worms for hours, i think i need a REAL woman in my life, not just mary jane), the leachate is NOT worm tea. The bottom of the bin often gets a bit soggy and anarobic, so the leachate might be full of phyto toxins. Either dump it back in the bin, the toilet or aerate the *intercourse* out of it. Trust your nose