Here are some tips to help get you started:
The new 851x315 pixel cover image will give your Brand more shouting space, but be careful about what you shout about... there are some rules....
Cover photos are 851 pixels wide and 315 pixels tall. If you upload an image that's smaller than these dimensions, it will be stretched to fit. The image you upload must be at least 399 pixels wide.
COVER PHOTO RULES
Your Page cover photo MAY NOT include:
A. Price or purchase information, such as “40% off” or “Download it at our website”.
B. Contact information such as a website address, email, mailing address, or information that should go in your Page’s “About” section.
C. References to Facebook features or actions, such as “Like” or “Share” or an arrow pointing from the cover photo to any of these features.
D. Calls to action, such as “Get it now” or “Tell your friends”.
Covers must not be false, deceptive or misleading, and must not infringe on third parties’ intellectual property.
Page profile pictures are square and, depending on the size of someone's screen, display at 125x125 or 150x150 pixels. The photo you upload must be at least 180x180 pixels. Uploading a square image of your brand's logo is recommended. Rectangular images will be cropped to fit a square.
Page profile pictures display next to your Page's name around the site, so yours should stand on its own to represent your Page. You can also be creative with how your profile picture and cover photo go together. On your Page's cover, the profile picture displays 23 pixels from the left side and 239 pixels from the top of your cover photo.
Quick Links for more info:
Facebook Pages/ Explore Popular Features
Interacting with Pages
Facebook Pages Video Guide
Pages vs Groups & my personal account
Facebook Pages community forum