One of the things that I haven't seen mentioned yet is that for mechanic changes you can drip feed the new rule sets one per session with tailored encounters to make sure they come up that session. After the players have experienced it you can talk together to see if it is working the way you want and if you should keep, tweak, or cut the homebrew rules. Then for the next session you can introduce another new set of rules. That way people can ask their questions about the rules and only have to learn one new set of rules before each session.

For anything that fits in a list or is only relevant to some classes/roles such as expanded feat or spell lists letting the players see it in advance so they can build around it would be appreciated in my groups.