This is an example signup sheet for a guild raid. Make a copy and customize it to suit your game, then create a secret link (via "add user") and share it with your guild.
Here's some other things you can do with the list: use the comment feature to help coordinate things; add an image field which screenshots of all characters; add a custom URL field to link to their online profile; use the bulk edit feature to clear out the responses and uses before signups begin for the next raid; group the list by class to make sure you have a good balance for the raid. And more!