Best way to go about biasing a Class B audio amplifier?
Your schematic is squished too small so that part values and designators can't be read, so I'll only answer in broad terms.

For starters, the input section is missing a deliberate DC bias.  You have AC coupled the input, which makes sense for a audio circuit, but added no deliberate DC bias of its own.  Only the middle stage has a deliberate DC bias, but this is AC coupled to the output stage so that bias does not follow to the output.

This circuit also can't seem to make up its mind whether it is meant to be single supply or not.  The three stages seem to be running from a single supply, but then the output is shown DC coupled to a load to ground, which makes no sense relative to the other parts.

To fix this mess, I'd start by adding some DC bias right after the input capacitor.  That should float the first stage at some reasonably predictable operating point.  Perhaps you can DC-couple the second and third stages, then use the DC of the output to bias the second stage.  This feedback would be filtered to only effect the DC operating point.  The AC feedback would still go back to the first stage as it does now.  Beware of instability though.

This kind of output stage will have a little crossover distortion.  You didn't give enough specs to determine whether that matters in this case.  If this is meant for high quality "hi-fi" operation, then you need to deal with it.  If it is meant for something less demanding, like a public address amplifier for example, then the overall feedback may deal with the crossover distortion well enough.  It won't be large, and for many basic applications that will be good enough, which allows keeping things considerably simpler.

In any case, you need to add small resistors in series with the emitter of each output transistor, else you can get large currents thru both and thermal runaway.