In the C13b9 example, you'd be on the lookout for C, Db, E, G, A, Bb.
The chord quality is different from the voicing, of course, but if you can identify that you're hearing a C13(b9) chord, then you'll immediately have some candidate notes to try and listen for. This really is the first step, and it's already been mentioned by others.
In many jazz piano contexts, the lowest note in a piano voicing will rarely be the root. Transcribe the lowest and highest notes of the chord voicing first, as these are usually the easiest to hear.
In addition to the tips described in other posts, here are some common techniques:
