Heraldry is a complicated system, with many rules and exceptions to most of them. But, it is not that hard to learn.
Here is an on-line tutorial that I found very helpful. The last few lessons are just outlines. I hope the author gets around to finishing them.
Here is a wonderful dictionary of heraldry, published in 1894. Someone took the trouble to scan and type it into a Web site.
There is also a wealth of good information at the SCA Heraldry page.