The one sheet is a cheat sheet for you when you pitch, but it is also someone's only glimpse at your novel. These are so great to have at a conference.
Make it eye-catching, something an editor or agent is drawn too when they look through their stacks of one sheets. Use graphics that will stick in their mind when they think of your book. I'll give you my personal tips on creating a one sheet based purely on my graphic background... As I am unrepresented and unpublished, I will have to let you know how mine works at this year's conference! :)
Raison d'etre: Everything should have a reason to be... This is the anal architect in me. I cringe when I walk into a room and a picture is just “floating” on a wall when it could easily have been measured out and placed in a logical spot. Make sure you don't have graphics or text “floating” in space. Line text up with other text, center it with something, make sure your graphics or bio pic aren't just placed in a blank spot, but work with the rest of the sheet.
Tip: Photoshop has a grid that you can turn on while working on a design. This is a great way to “place” your elements.
Anchors Away: Use gradients, blocks of color, or "watermarked" graphics to anchor your sheet. The one sheet is just that, one overall composition to represent your novel. Be sure you don't just leave the eye “hanging” by keeping all your graphic work at the top or at the bottom. The graphics and text should flow to completion together.Balance is everything. You don't have to have a ton of graphics, but if you have them, be sure they aren't sticking out amid a sea of text, that will only take away from your text.
Tip #2: How to put a picture behind the text: In a Microsoft program or Open Office, you can right click on an image and go to "order" or "alignment" and it should give you the option to send "to back" or send "behind the text". Be sure you change the opacity on the graphic so your text is still clear. In Photoshop or Gimp, you just make the graphic layer below the text layer.
Tip #3: DON'T RELY ON Photoshop and GIMP's text tools...make your one sheet background, then insert it into a Word file and use text boxes. The text in these programs (perhaps newest versions of Photoshop are different?) does not print out as crisp as Word.
Artistic License: It is easy to become overwhelmed with the many clipart images and photos you can choose from to represent your book. Don't settle. Only your mind's eye knows what you envision when you think of your story. Is it the vibrant colors of your humorous heroine's shoe collection? Or deep reds and velvety purples of kings and queens? Allow the graphics to support your novel in a way that the front cover of a book would. Be picky, take your time, and CREATE!
Tip: You can find a ton of free pictures using Flickr Be sure to check what each photo's copyright rules are...they will let you know how much you can manipulate it, and if you have to get the photographer's permission.
Go here to see examples and content tips on one sheets:
Rachelle Gardner's One Sheet Post
Dineen Miller One Sheets
Are there any specific graphic-related questions you have as you create your one sheet?