I trust that you meant "new trapshooter" when you stated "new trapper" in your initial message.
I highly recommend Trapshooting Is A Game of Opposites by Dick Bennett. The 122-page book (At least, my version of it has that many pages.) covers: guns, mount and fit, use of the eyes, swing, foot positioning, doubles, handicap, and a few other topics. Dick Bennett explains and summarizes in an easy to read fashion. Of course, other shooters will recommend other books and videos (e.g., Leo Harrison, Phil Kiner); however, I recommend starting out with Dick Bennett before graduating to other sources including the Shotgunworld.com forums or videos on the web. As you will experience, free advice (including mine at times) may only be worth the amount you pay for it.
Honestly there is a lot of good material on YouTube that is free. Nothing beats the progress you can make working with a coach. Sometimes expensive, but can be the quickest route to results and saves you from starting off with bad habits.