I think they're actually pretty easy. Apparently you need twice as much brown (carbon based like paper, leaves, straw, ie things that break down dry ) to green (grass clippings, fruit & veg scraps, ie things that break down wet), best to layer them so it's evenly mixed. Chuck in a handful of organic fertiliser, or some blood and bone or some seaweed solution (apparently it gets the microorganisms going a bit faster) then fork it over as often as you can stand doing it. The more turning it gets, the quicker it will break down. If it seems to wet and gluggy, then add more brown, if it seems too dry, add more scraps/liquid organic fertiliser. Keep going until you have something which is near the consistency of lovely brown soil.

BTW I've never heard about the onion skins, we put them in, and also egg shells too. Avocado seeds and sweet corn cobs are probably the only things that don't break down at the same rate as everything else. I think the onion thing is for if you have a worm farm. The worms are fussy eaters LOL