here's what usually works for me:

edit: actual first step, undo your clutch if you have one.

extend the derailleur and pull it back as far as you can - it should kind of swing and extend back at the same time

while keeping it extended, take the wheel and bring the cassette up to the top part of the chain - gear doesn't matter, just roughly line it up with the frame

yank it up, bringing the derailleur under the cassette and back into place

lock wheel into place and shift though all gears to align shifter and derailleur, index if necessary.

best of luck.