No doubt, there are plenty of people on here and sites you can read to learn all about breeding. I just want to add and ask that you look at each of these threads so you can go into breeding with the full knowledge that you may be risking the life of your dog.
These are just the recent deaths after childbirth, there are countless others on here and countless more whose stories will never be told.
Pony Tail
http://www.yorkietalk.com/forums/showthread.php?t=58303
Lily
http://www.yorkietalk.com/forums/showthread.php?t=57387
Reggie:
http://www.yorkietalk.com/forums/showthread.php?t=37520