Hi Dude,
Welcome to TU . As an introduction to making crankbaits I reccomend this article by Skeeter. It will tell you what to look for in a handmade lure:
http://www.tackleunderground.com/board/viewtopic.php?t=3058
Here's a link to the forums search: http://www.tackleunderground.com/board/search.php Try searches in the hardbait forums on words like "foam, featherlite, mold, rtv, wax" these will bring up a plethera of info.
The crankbait mold in my tutorial is designed to hold the thruwire on pins suspended inside the mold cavity. A thruwire should always be centered for balance. Ballast placement all depends on lure shape but for the most part they are centered just above the belly hook mount or slightly forward. Again... this is based on lure shape. For more info on ballasts do a search on "xray, x-ray, autopsy, autopsies"
Rattles can be fashioned from pen tubes, 22 shell casings, glass chistmas tree lights almost any cylindar. I use bic pen tubes and bb's. here's a link to a post on rattles and foam lures:
http://www.tackleunderground.com/board/viewtopic.php?t=7014&highlight=foam+featherlite
And a link to Cheeseheads tutorial:
http://www.tackleunderground.com/board/kb.php?mode=article&k=10
You can pm me with any q's ya might have. Post pics of your lures when you get a few done and remember to pay it forward to the next newbie.
Tight Lines,
Shawn