Here is what works for me on my Avid Hydraulics
Remove the wheel
Remove the pads
Push the pistons back into the caliper using tire levers or large screw driver
Insert pads
Loosen adjustment screws on caliper
Put the wheel back on and tighten skewers with the weight of the bike on the skewers
Slide a business card between the rotor and pad on the side that is rubbing
Without squeezing the brakes, tighten adjustment screws. Once you feel resistance, alternate tightening top and bottom screws a little each time
Set the pads by squeezing the lever with the biusiness card wedged between rotor and Pad.
Once the pads are set, remove the business card
If its still rubbing, try loosening the skewers a little.
