Originally Posted by zymphad

There are great videos on youtube for rear derailleur. First step is to set the limits. Bottom make sure it gears properly on smallest cog. Then on largest cog, make sure when you pull the cable hard, it doesn't drop off the cog. There are labels on the deraileur, H and L. L would be the largest cog. You don't adjust the shifting with those screws, those are just the limits. For example that large plastic you have behind your largest cog? It's not needed if you have the limits set properly. You adjust the deraileur with the micro-adjuster, turning thing you see to the left of the deraileur. You can put the gearing into the middle cog and adjust it in the middle from there. Then you just shift up and down until it's smooth, adjust a quarter turn at a time.

If you can get it to shift fine on the one half of the cogs but not the other half, that is indication that your hanger may be bent. Cost me $20 to have my hanger adjusted at a LBS. It was worth it. Even a slight bend can affect your shifting.

For me at least. If you can get it to shift one way fine, but the other way it hangs a bit or causes issues, that indicates to me the chain is in the wrong direction. Shimano chains are directional.