Prissnboot sent me a Pm asking for my experiences so here goes:
Use an album block, such as Album twist, Album block, Album Patch, Album Star, or just a Snowball blocks works too.
Here are links at Quilters Cache:
http://www.quilterscache.com/A/AlbumTwistBlock.html
http://www.quilterscache.com/A/AlbumBlock.html
http://www.quilterscache.com/A/AlbumPatchBlock.html
http://www.quilterscache.com/A/AlbumStarBlock.html
http://www.quilterscache.com/S/SnowballBlock.html
I use a good quality muslin for the signature area, cut the
signature area larger than needed to construct the block.
Iron freezer paper to the back of the fabric, this does a couple of things. It makes it easier to write on, the fabric won't stretch when people put pressure on it, it also keeps the ink from bleeding. Sometimes, when people write on the block they put too much pressure and it causes the ink to be too heavy and bleed.
Lightly draw on the fabric the size square you need, including the seam allowance, to indicate where the people should write. These markings will be hidden in your seam allowance.
If you want to get real prissy, you can draw lines on the freezer paper to give them a guide to write on. I run the sheets through my printer, print on the paper side, and usually it is dark enough to see.
Use a good Pigma fabric pen, it's important, lesser quality won't hold up. Be sure to heat set the ink!
Here is a link, there are also fabric crayons here.
http://www.quiltbug.com/notions/marking.htm
There are 2 ways to approach getting the signatures:
1) have the squares at the event to be signed. This way you can control everything.
2) mail the squares to everyone prior to the event, with a return envelope and instructions. The only problem with this is you end up chasing for the fabric, believe it or not!
But the advantage is that you can have a completed quilt at the event.
3) complete the quilt before the event and obtain signatures at the event. Disadvantage here is if someone messes up the ink, the quilt shows it. At one bridal shower where I premade the quilt, a lady shook the pen and splattered ink across the whole quilt. My heart was broken, but the bride was thrilled anyway. She still has the quilt hanging in her bedroom, ink splatters and all!
If I think of anything else I'll add another post.
Good luck, keep us posted on your quilt. We would all love to see it.