Crossword Compiler 8.0 professional bundle is a good place to start. Next, when you pay for the Cruciverb membership, you get access to a wordlist which has all the entries used in major puzzles for 25+ years. Plus, you can get access to the Ginsberg clue database (free). By signing onto the Cruciverb-L maillist you can request a mentor, and one will usually step forward (if not too swamped). The mentor can also supply a decent starting wordlist which is better ranked than others that are available. As far as learning the trade, I got a lot of mileage from the advice given in Coral Amende's book "The Crossword Obsession." There are tidbits of construction advice that is scattered throughout that book. Also check the Sage Advice on this website.