Off Site Power Checks
You can plan based on where you're going and what the weather is, but you can bet that it'll change by the time you get there.
I'll do all the planning I can before I go, but I've found the off site power check is a good way to make sure you've still got the power before you commit to the approach. I use it with confined area/ridge line approaches and rappel ops, and I do it before every approach, even if I've been going in there all day.
When I set up on a long final I slow the helicopter to an OGE hover while I still have sufficient power to fly out of it, if I find I don't have the power. If I have the power to hover out there I should have the power in the hole. Keep in mind that things can change when you get close to the trees or the ridge. Winds defy physics some times, and the wind that's been helping you above the trees can drop to zero or shift to a quartering tailwind below the tops.
Departing a confined area I'll depart vertically until I'm above the obstacle so that if there's a problem I can go back down to a known spot instead having to bleed speed to land short of the trees.