Generally, stronger smelling weed is better; although this isn't always true.

Not sure about the size of buds question; see http://boards.cannabis.com/showthread.php?t=45246 for what some pretty good stuff looks like.

The seeds look like seeds and the stems look like stems. If the seeds are white, it's not a big deal if you accidently smoke some, although it would be better not to smoke any seeds. You shouldn't smoke the stems. You should be able to tell what the stems are.

If you are smoking a J, you want to break the bud up and grind it some. If you smoke out of a bowl, it's really just personal preference.

I most likely don't know what the fuck I'm talking about, so somebody correct me if I'm wrong. I just noticed nobody replied and decided to give what help I could.