I guess I will share some stories and thoughts.
The best community for selling gear in is the Audiophile world. There has been very, and I mean very, few scum bags. It is more like a gentleman's club. I have sold things I made for a bit over the price of what it cost me to people in Europe more than happy to pay the big shipping because the parts are nearly impossible to get there. They would essentially have to pay international shipping charges ten times over to get just the parts, then be charged higher rates for many of them because of who actually ship to their part of the world. (I am a DIY audiophile because I am freaking poor, too poor for Leicas) I have also sold many other things that were DIY audio stuff, some kits that I put together and sold for about what the kit cost.
The worst thing that happened to me was shipping an expensive turntable I bought with money from having a high paying job one summer. Apparently I was confused mentally to the point of being drunk when I packaged it. This was at a high stress and unhealthy time in my life. I ended up losing the turntable and around $500. The buyer hated me. Was it my fault? Yes but not in a way I could have done anything about at the time.
Selling specialty items is the best. I have made a couple thousand dollars selling equipment a lumber mill threw out (well sold for like $100) on Ebay in the industrial side. These people would be in trouble lawfully if they screwed up their own books let alone with me. That money payed for one semester of tuition and some rent. The point being the, more specialized the more likely your customer is to not mess with you. It is not worth selling overly generic items on the Internet that are worth nothing unless they are hard to come by and you want to do someone a favor, like RFF members.
One of the biggest problems is when people make a poor purchase to begin with, point blank period, double over, under, around, in your face, this is the one thing you need to avoid. If what you own is in good shape, and was worth less or equal to what you paid for it then you can expect to get an equal amount of money out of it. This is a clear complaint here. I have to say buying cameras online SUCKS. I want to pay the least amount of money because unless you get to see it in person you never know. Therefor you need to ask as many questions as possible to not get ripped off. By doing this as much as possible and feeling the most confidence in what I own and pay money for I am always able to sell stuff off easily when I need money. It sucks because I like to own things but I am poor! It is unfortunate that people always want their gear to be worth more than it is... Ebay is making it that way. Professional sellers are increases the prices of everything so long as there is a low number of the item available on the Internet. For example my Nikon F Apollo FTN (will be in classifieds tomorrow or when paypal get around to transferring) on Ebay is worth $450-550. If I listed on it I would sit on it for probably 6 months before a sale.
The smartest sellers are estate sellers (sometimes). They have bulk quantity of items so the margins are unimportant in many respects. The sell cheaper than anyone on Ebay, but not low enough that you can make money off of it without setting on it for 6 months or better.
I bought a Nikkormat FT for $70 but did not ask enough questions and now I have a junker. The guy thought he was being honest, and it would of made sense if the lens was in good shape... I paid shipping because it was a town over on craigslist. The problem is not that he was trying to be dishonest but the fact he had not investigated the camera enough, but would have if I asked.
How to sell on RFF, and what to sell.
First do not ever sell to anyone that has a shotty story and no posts. Only sell to people that regularly post and do not want to be booted from the forums.
Sell your expensive (couple hundred or more) investments based on how quickly you want it to go but always start at 75% of Ebay's lower buy it now (equivalent condition) price for fair value, or less for a quicker sale. (this is what estate people do basically)
In your post make it clear that international people are going to pay full on outrageous shipping costs plus a handling fee for your annoyance of filling out a dozen forums. Basically they are going to pay out the a**, so they better really want it.
Let the seller know every flaw no matter how insignificant it may be - all of which you should of been aware of at the time or purchase.
Ideas for breeding good community on the RFF classifieds.
Obviously no sales to people with no regular post contributions or without a great story. Keep a personal vibe to it.
Give things away to people that have a reason for owning it, when you are in a good position to do so... If your budget is tight then ask for shipping, packaging, gas, and $5 handling fee (probably will never come out to more than $20-30).
Group items worth little but as a bonus, and that cost money at dealers with equipment to breed good karma and friendliness. It cost you nothing, but would cost the person $10-20 to buy. You can not sell the items due to fees, at the low price. It is just a nice generous thing to do.
The more inner-circle trading, giving away or at good prices, the friendlier the place gets and the more likely you are to benefit from it by people preferring to buy from you or reciprocating a good deal.