Let me know when you can come generally in any given week.  example

I'm available evenings by around 7pm.  Tuesdays I can't get on until after 9pm and thursdays I can't come at all.  I could commit to two evenings a week, with a possible third day if it's going really well and we want to push.

We'll be picking two days every week.  I'd like everyone to sign up for these days.  Raiding choice will be based on past attendance and gear.  We might swap people out for some fights.  ie: if we have a few rogues who want to come, we'll put them up for moroes, then swap them out for ranged on maiden due to how that fight works.  This is assuming we get more people then we can use which hasn't happened yet.