I can give a tip that is more related about what not to do than what to do and that is to change strategy mid hill. Whenever I've done that it has not worked out well. Either stick to attacking the hill with power or decide to spin up it.

The one piece of advice or tip for hills is to keep doing them and doing them, eventually it does get better. When you are feeling particularly strong is a good time to go do the hill that you have avoided. You may surprise yourself.

There have been a lot of good tips here, good thread!