Be careful of misting. People think this is a good idea, it is not. Water on the leaves does 2 things. It causes scorching when using HID lights (CFLs less of a problem but no sense getting into bad habits) and also you will suffocate the plant. Each leaf breathes, it needs a constant supply of CO2 and if it is wet, it doesnt get as much of that needed CO2.
When watering your plants, water only the soil, underneath the lowest leaves. Humidity is very important, but not at the cost of spraying your plant. For seedlings, use a propagator, or a dome over the pot. It keeps the humidity high but without beading water on the leaves. Remember seedlings only have 2-4 leaves, and these are its lifeline. Heated propagators are very cheap. I got mine for £15. Getting humidity in a closet or tent under HID's is easy, very easy. Simply keep a steady temp of 25 degrees C and normally the humidity fixes itself. If it drops, i just stick a bucket of water in there and the light evaporates it for me, raising the humidity. Simple. Just make sure your temps dont drop.
Humid and cold = mould.
Humid and hot = pot!
I made the mistake of potting up too early. I would wait until you have 4-8 true leaves (not including the rounded starting leaves) which is about 2-4 nodes. Be prepared for your babies to stop growing for weeks while they explore their new pot and build roots. Dont use any nutes until you have at least 8 leaves (4 nodes), and bring them into it slowly. 0.25 EC increase per week is a good pace. Rain water is about 0.6 EC on its own, so in 4 weeks you will be at a good level. But only start nuting when you start to see a change in growth rate from extremely slow to a faster paced growth after transplanting for the first time.
Just remember, you will make a bucket load of mistakes, we all do, so take it slow, take it easy, and dont rush your babies. You are not going to get from seed to harvest in 12 weeks on your first try. May take 18 weeks, but your second time round will be quicker, you will know more, specially how your strain responds to certain things, and you will start to become an experienced grower.
Good luck buddy, the first 2 months are always the most stressful =)