Start booking well in advance. The good ones book up fast. Just about any performer can be located from this site. The WUMB web site has a list of all the Greater Boston coffeehouses. Check out the links to the coffeehouses to see how they do their web sites.
Most performers have web sites with streaming audio and lots of PR-bio material.
The material for the coffeehouse's web site can be copied from the artist's home page. The coffeehouse's web site should link back to the artist's site. The material can be used to generate the schedule web page and the coffeehouse flyer. Start collecting names of attendees so that flyers can be sent to customers to tell them about upcoming shows. The schedule for sending out flyers varies with the coffeehouse.