Identifying a glass or china pattern can be an extremely tedious process. When you are first starting out, the best thing to do is visit your local library and start flipping through some books.
If you are lucky enough to have identified the maker of your piece, you can narrow your search considerably. If you have no idea who made it, identifying a pattern can be a bit like trying to find a polar bear in a snowstorm.
It is extremely important that you match your pattern EXACTLY when you are identifying it. A slight deviation in the design may mean that it is a completely different pattern entirely, or possibly even another manufacturer.
Look for a book that has detailed photographs and drawings (especially for glass patterns which can be difficult to see in a photograph). A price guide might be useful in determining the value of your piece, but remember it is only an estimate. Color, condition, and many other factors influence value.
Many china and glass collectors' clubs maintain excellent websites that can be very helpful. However, you must exercise caution when using the internet to do research. Be careful who you trust, because anyone can write anything on a website. Look for legitimate collectors' groups, and be wary of any information you obtain from someone who is selling a piece. They may or may not know what they are talking about.
These are some useful books I have used to help identify patterns in my museumís glass and china collections: