You need to be pedalling forward when you're shifting or the chain on the cogs will resist your efforts to shift to a larger gear. So you'll want the bike to be held up or flipped over or something so you can spin the pedals while setting limit screws and adjusting shifting. Also note the FORWARD. It won't work if you're just backpedaling.
If you haven't done it this way already you need to start with setting things up for the smallest cog at the rear and ring at the front. with the derrailluer sitting at this "relaxed" point set the small cog/ring limit screw so there's no noise. Now pull the cable end tight by hand and secure it with the clamping screw. Click the shifter up ONE click and play with the barrel adjusters on the cable stops and at the rear derrailleur until it shifts cleanly. Check it back and forth a couple of times. Try some other gears. Slightly adjust until it shifts as well going up as it does coming back down. On the front it's mostly about shifting up and down smoothly and then trim it so it doesn't rub on the sides of the derr. cage.
It also really helps to check out those great online resources that come with pictures.
www.sheldonbrown.com and the Park tools website procedures area.