Here's my advice, I have like 99% success these days, and I keep it simple.
Do:
Take the right size clone. I usually go for something small enough to fit into a solo cup, but still has at least two nodes.
Use cloning gel and/or powder (I use both)
Rough up the base of the clone where you cut it a little bit (I cut a little vertical slice)
Dip it in water as soon as you cut it, then the gel and then the powder.
Trim the leaves / cut off the tips. I just leave a few leaves at the top and trim up the rest at the bottom.
Stick it in soil
Leave it in a low light area like the bottom of a veg tent or under a single cfl bulb. Nothing bright, you want root development, not leaf growth...
Spray it with water for the first few days to make sure it doesn't wilt. Keep it in a very humid place.
Leave it alone for at least two weeks. Just add moisture and water as needed to the soil.
Don't:
Mess with it! Don't check for roots, ever! This is the #1 thing that I did wrong. If the clone wilts after a few days, you don't have enough humidity, and/or the clone is just dying.
If the clone doesn't die and just sits there and does nothing for a week or two or even three, then great! It's working on roots. After 1-3 weeks you should notice it starts to perk up even more and maybe even start growing a little. Time to transplant into a bigger pot and start your grow.
So in summary:
Don't check for roots! Leave it alone! The correct way to know your clone has roots is to just wait it out, and see if it dies or not..
I usually know after a week if I have a good one or not. Most clones that don't take are wilting and dead after a week...