Originally Posted by FBinNY

What the others said with one caveat about chain tension. Newbies have the tendancy to over tighten their chains, especially if their bikes are wquiped with chain tensioners.

A chain needs to have a bit of slack to work properly. Holding the wheel steady you should be able to have a bit of free play in the cranks to transfer that chain slack from the lower to the upper loop.

If you pull the wheel back by hand it usually works out fine, but don't use chain tensioners like jacks to pull all the slack out of the chain. They're not really chain tensioners, but rather anti chain tension retainers to keep the chain from pulling the rear wheel forward.