One thing I like to do (keeping in mind that I am not a great copywriter myself) is to simply study and reverse engineer what all the big dogs (who are presumably putting money and time into testing and hiring great copywriters) are doing in their sales letters, emails, or whatever else.

I have a separate email account where I am subscribed to most of the big IM gurus and known copywriters out there and every few days I briefly peruse their emails and see what they are writing, how they are writing, how their emails build on each other etc. Each has their own style but there are similarities across all. I do the same thing with sales letters on all of the major launches.

There is nothing wrong with using tried and tested copy examples as inspiration and education for your work.

As for Jay...

Cashvertising by Drew Eric Whitman
Influence - The Psychology of Persuasion by Robert B. Cialdini
YES! - 50 Scientifically Proven Ways to Be Persuasive by Noah J. Goldstein

I will pick those up...thanks for the share!