Here is the thing, if you are really serious about this, find a line of dogs that are breed for this purpose. It will makes things much easier. Like some people say, any dog can be trained, but some dogs can excel. If you get a dog that is guaranteed (money back) to track, you will be better off in the longrun. Puppies can be trained very early.

Check out this site, there is also a forum there that deals with tracking and there are people there that can help you select a breed and maybe help you fnd a breeder:

http://www.thetroutbum.com/hundesideulv.htm