Here's an excerpt from Produce, Publish, Publicize discussing bookmarks:
The bookmarks and posters are very important parts of promoting yourself. I suggest leaving 30-60 bookmarks and a poster one month in advance for each book signing location. The bookstore will typically put the bookmarks on the front counter and let customers take them. It’s great free advertising for them and it’s a minimal investment for the author. If you are computer savvy, you can make them up rather quickly. I shoot for 5 bookmarks on a full page when I’m advertising an event. For generic bookmarks, I shoot for 20 bookmarks on a page.
On my website under Writing Advice > Marketing, I have a sample bookmark page attached. Notice the cover image is on the bookmark. You want people to know which book they want to buy by sight. The title and the author’s name is also listed below the book in case the writing on your cover ends up too small to read. This avoids any confusion. There is also an advertisement for the event listed. You may opt to put a very short book summation here instead but I find an advertisement for the event more effective when you have a book signing to advertise. On the back, have short blurbs praising your book. Since you have this guide, you know pre-publicity is key to a successful campaign and have already gathered endorsements before setting up your event!
Now that you have your bookmarks designed, print the bookmarks on nice glossy paper. I have found that photo paper is durable and it looks more professional than regular printer paper. Cardstock would be another option for an author doing bookmarks him or her self who does not want gloss. If you watch your local Target-type stores, you can find packs of 100 sheets of durable paper on sale for $10.00. You can also find it on theInternet inexpensively.
You want a nice printer to print the bookmarks. If your printer leaves lines or a grainy look, consider going to Kinkos or another printing shop. Last I checked, Kinkos charges $0.50 per color sheet. For 30 large bookmarks, you’ll pay $3.00.
There are also many companies online that will print bookmarks for you if you don’t want to make your own. Do a google search for “buy bookmarks” and you will find many options ranging in all sizes.