Inverting op-amp amplifiers are very easy to use. This circuit highlights an improperly biased single rail amplifier (top) and a properly biased single rail amplifier (bottom). The difference between the two is the DC operating point applied to the noninverting input. Since the op-amp is effectively trying to make the + and - inputs equal to each other adding a DC bias let's the signal oscillate around some point the op-amp is able to supply voltage at (in this circuit 0-12V). Adding the input DC blocking cap is very important as is the DC blocking output cap. These keep DC currents to a minimum and your op-amp happy. As well as keeping other stages from going kaboom from DC bias mismatches.
Note: These are unity gain amplifiers
