I think it would be a good idea to have a set of rules for posting for sale threads in the Classifieds subforum.

For instance:
1. Must include a price.
2. Must include location of item.
3. Must include photos (some forums even make members include a photo with their username and date somewhere in the pic).

This would make things so much easier than having to constantly ask sellers to post pics, tell us where they are, or even how much they want...

Warnings should be given to OPs who don't follow the rules and then threads deleted if warnings are ignored.

^ I do like those ideas. Those are the most commonly asked questions, and should be common courtesy... but they're not, unfortunately.

I would also add that it might be a good idea to automatically lock older posts, if that's possible with the forum's software (but only in the buy/sell/trade section). Maybe have the cutoff at like 3 months? Only the original poster can bump it to prevent it from being locked (if stuff is still available). There are new members bumping up posts from almost a year ago. You never know when someone still has something sitting around in their garage because it never sold at the time it was posted. But someone can always just send a PM and ask, rather than have the old topic bumped up.

I see this happen often enough to suggest curtailing it.

1) NO e-bay links (usually ending up dead link after the auction is done!)
2) NO craigslsit links (same as above, especially if it is NOT your items!)
3) When your items are sold, MAKE SURE to delete the post - or send request for deletion to mods...simple.

I've been cleaning up so many posts here for all the dead links (e-bay, craigslist).