Forgive me if this is telling you stuff you already know.
- I think the #1 tip for hill-climbing is don't back off. There's always a temptation when climbing a hill to ease up on the pedals for just a second. Don't do that. You lose all your momentum, and getting it back is more work than it's worth. The hill winds up being much more work after that momentary break.
- Maintain cadence. This is not possible with extremely steep hills where you're standing on the pedals, but in general, shift through the gears steadily so you can keep your cadence in a reasonable range.
- Each hill has its own logic, and with hills that you ride regularly, you can figure out "here's where I stand, here's where I shift into the 15, the 17," etc.