Hints on how to sell on A'gon?

What they said. Good advice above. I would add, a simple honest description has worked best for me. If it has a few marks on it, be honest about it and try to show them in the pictures. People want to know how it works, how it looks, and that it has been well taken care of, hence all the ads that say "no smoking cats have used these speakers!" :^) Finally, price it fairly (check out the A'gon bluebook)and don't get overly anxious if it doesn't sell right away. I have had stuff up for several weeks without an offer, then received three offers in the matter of a couple of days.

Good pictures, good feedback, honest description, and what are other people asking for the same piece. Has worked well for me...

This is not Ebay in that most respondents already know the intrinsic value of item(s) up for sale. Thus, the seller can set a reasonable price on Agon with less risk of underselling. Seasoned hobbyists also know what is a "classic" within their own fields of interest.

Generally, mid fall and winter ads are more productive. Sales fall off when the weather warms and around Xmas. My personal turn off is the ads that link to a well known web site where you can bid on "it". And the classified and auction for the same item.

In addition to all the good advice above, decide for yourself very clearly what your bottom line is before you post a price. You'll get an amazing variety of offers with infinite variations asking if you'll accept a lower price, pay the shipping, split the Paypal fee, etc. It's fine to be able to factor those things but unless you know what you're willing to accept, it can be maddening.

It's inevitable that someone will make a lower price offer, especially if you mark the ad OBO, but you're not under any obligation to give the person an answer immediately. It usually works well to tell the potential buyer that you'll get back to them if that's the best offer you receive. If they tell you it's 'take it or leave it,' leave it.