1. Catching a wave
You need to be paddling with maximum speed, a good technique tip is to imagine you are paddling over a barrel and this forces you to have a higher elbow and hence dive deeper. Your strokes need to be quicker than normal paddling. Keep your head as still as possible: Kelly Slater is a good example of keeping his head still whilst paddling: https://www.youtube.com/watch?v=bwFBojLeUt8
Try to lean your head down as you catch the wave, try to almost bury the nose of your board and kick your feet for the last few strokes before you catch the wave.
2. Paddling back out through white water
You still need to paddle strongly and duck dive deeply, try to pick rips back out whenever possible. Still use the paddle over a barrel technique.
3. Paddling back with a rip or outside of the wave breaking area
You can relax your arms by throwing your arms forward and not bringing them very high out of the water rather than the paddling over a barrel technique. John John Florence is an excellent example of this: WSL Carona Bali John John Florence Replay at about 9:50 minutes.
This allows his arms and shoulders to recover.
** Many surfers have shoulder issues at some stage and this could be due to over-straining their shoulders whilst paddling. **