While writers agree that classes are a valuable source of professional development, for many spending hundreds of dollars to attend a writing retreat is too high a price for inspiration. Also there's the challenge of explaining to your significant other that you're leaving him/her with the kids, chores and pets for the entire weekend while you commune with the muse.
Much of the value in seminars is the opportunity to learn tips of the trade from published writers. Through attending book signings, I’ve found much insight can be gained in about an hour’s time for less than $20.00. I’ve even attended book signings with a child in tow which ups the initial investment at the cost of another book or a post-book store milkshake. Have a few key questions in mind as you hand over your book for signing. If you happen to stop by during a lull, you can extend the interview.
Avoid the multiple question approach with a well-known author, particularly if there is a long line behind you. Monopolizing his/her time won't endear you to your favorite author and causing a riot at Borders could derail your career.
If you have the opportunity to attend a writing seminar, go for it. Learning from others is essential to any art. However, if you are strapped for cash or time, consider book signings as an interim option.