Hydraulic Disc Brakes Maintenance I have Hayes Nine hydraulic disc brakes on my mountain bike. I have recently replaced the brake pads and after that it seems that the pads are almost touching the rotor. 
How can I adjust it? 

I have come across the term "bleeding the brakes", but not exactly sure what it involves and if it applies here. Is it complicated? any special tools required?

On my previous bike I had cable disc brakes and the maintenance was pretty straight forward, but the hydraulics seem like a black magic to me.

Thanks
You need to bleed your hydros when they get a squishy feeling. They should be pretty close to the rotor, but if they are rubbing a lot, then you could try to recenter the pads around the rotor. 

To do this:


Loosen the bolts attaching the brakes to the fork (or the adapter). 
Grab the corresponding brake lever and hold it in place. You can use a rubber band for that, and it will free up your hand for the next step.
While the lever is held, the pads are pressed against the disc. Now tighten up the bolts you just loosened.
After you have tighten them back up, release the brakes. Spin the wheel to test if the discs still rub.  You might need to do it again, but this should minimize the amount of rubbing.