It's important for the liquid you wish to carbonate to be very cold, the CO2 dissolves much quicker that way. So it takes a little planning, bottle in the fridge overnight. I generally use 1 liter plastic beer bottles. Put on the cap with valve, squeeze the bottle to remove any air, tighten the cap. Then I hit it with the CO2, a little more than 10 psi though, shake like the dickens for 15-30 seconds, turn off CO2. Put bottle back in the fridge to rest, preferably for another 24 hrs. Then bleed the valve & put on a regular bottle cap. Does take time. I've been planning on making up a few additional caps with valves so I can have more bottles ready faster.
If you're just carbonating water, there's usually no need to let it rest too long after carbonating.
http://www.youtube.com/watch?v=4AQi9...eature=related