On my commute to school yesterday, my chain slipped off 3 times, only from my rear cog. I had it previously aligned by the lbs mechanic. So when I got to work on campus I tightened the chain and have had no slips yet, but the chain seems to not run as smoothly. The chain appears to be "clicking" at some points with the rear cog's teeth during a complete rotation of the crank. I can barely hear it when riding, but I feel safer now that the chain has not fallen off. But should I be able to trust my repair? Should I be worried about having the chain too tight?

Usualy a chain skipping off is because its not aligned. The clicking noise is now the chain catching slightly. I would take it back to the wrench to re-fix it.

A properly tensioned chain should not be able to jump off the cog. Did the wheel slip in the frame during your ride to school? That may explain why it was coming off. When you got to school and made the adjustment you may have made it too tight. That's why it is not smooth now.

To check chain tension:
Fing the mid-point of the chain between the chainring and the cog. You should be able to move it up or down about an inch in either direction. This amount of movement is subject to personal preference. You want enough slack that parts do not wear prematurely but not so much that the chain can come off.

A properly tensioned chain should not be able to jump off the cog. Did the wheel slip in the frame during your ride to school? That may explain why it was coming off. When you got to school and made the adjustment you may have made it too tight. That's why it is not smooth now.

To check chain tension:
Fing the mid-point of the chain between the chainring and the cog. You should be able to move it up or down about an inch in either direction. This amount of movement is subject to personal preference. You want enough slack that parts do not wear prematurely but not so much that the chain can come off.
Thanks for the info. It is back at the shop, getting it fixed correctly, which should have been the case in the first place, since they put on a new chain and said they aligned the rear cog to the front chainring. They better now charge me for the work that should have already been done to solve this issue.

When you get it back make sure you keep the chain well lubed. A dry chain may develope sticky links which adds to the noise and possible skipping.

When you get it back make sure you keep the chain well lubed. A dry chain may develope sticky links which adds to the noise and possible skipping.
Yeah, the chain is new and I hate the sticky stuff they put on it. It attracts so much dirt!