For consistency, the keys were 1) finding the correct grip every time and 2) newer strings. I restring every 6 hours, because things go crazy with the 1hbh after that. Forehand is fine with old strings, but the backhand is higher maintenance.
For power, key is court movement. You just have to be at the right place at the right time. If you're there early - even by a second - you can unleash the beast.