Check moisture levels
You can check moisture levels using the industry standard 'squeeze test' or if you want to keep your hands clean you can use a pot plant moisture meter.
The 'squeeze test'
To do the squeeze test plunge a hand into the wormery and pull out a handful of wormery contents from underneath the most recent additions. Make sure that all the worms have fled from this clump and then squeeze it, with the same amount of pressure you would apply to something like juicing a lemon.
If no water comes out - it's too dry. Add some water to the contents with a watering can and try again next week to see if it's balanced itself.
If a water flows out - it's too wet. Add some sheets of dry newspaper to the top of the contents, or for a more effective measure, scrunch up some newspaper into balls, or get hold of some shredded paper and mix it in with the contents.
If a few drops of water come out - it's just right!
You will find that a pot plant moisture meter will do just fine for checking your wormery is at the correct moisture levels. Readings of 7-9 indicate the right moisture levels for your worms. If too wet or dry follow the measures outlined in the squeeze test.