Suggestions for Auto-Responder Messages?

I have two questions about auto-responder campaigns. I've seen so many different things that I'm hoping someone here can slap some focus into me;). The presupposition here is that I have some opt-ins.

1. How many messages should I program in? 52 for 1-per-week? More, less?
2. What type of information should I put in these pre-programmed messages, typically?
3. Does anyone have suggestions as to how to best format these messages for e-mail? I use 1Shopping Cart and it always tells me (AFTER the fact) that I have exceeded the maximum # of characters per line for the text version, and something similar for html. But it won't tell me HOW to prevent this from happening or what lines are the ones that are too long. Frustrating.

Thanks!

Ken