Barracuda - Totally Driven!

I have Shimano rear cassette, Shimano shifters and Shimano rear derailleur:

If I find on a bike that the shifter's shift points do not perfectly align the derailleur with all the sprockets on the rear cassette, can I assume I need to shim between the sprockets on the cassette?

I would try a couple turns on the shifter's barrel adjuster to take up any cable stretch and then mess with the rear derailleur's adjustment screws to fine tune the shifting. Any number of minor issues could be the culprit... worn teeth, cable stretch, chain stretch, a bent chain link to be twisting the chain, or...

Good luck!!!

New chain corrected that issue..