Armslist.com and Gunlistings.org are a couple of places one can advertise. There is usually a local page for your city.
Not sure where you are at but here in TN (The Land of Shootin' Stuff) legally you can only sell to another state resident without an FFL transfer. I always ask for a DL or CCW permit. Legally I am also required to ask the individual if there is any reason they are prohibited from owning a firearm. A bill of sale is not required but I always state in the ad there will have to be one signed by the purchaser. The i.d. presentation and bill of sale requirement helps weed out shady characters.
I always meet in a public place (usually the gas station or grocery store across from the local P.D. or the local Sportsman's Warehouse parking lot (always someone there making a gun deal)) and take someone with you.
I've sold many dozens locally. Only had two bad experiences. I make it a point to walk around the back of their car. Dude showed up with a GA tag on his car once and I told him no deal. He got pissed and wanted to argue about it. I stated the law's the law and I wasn't going to jail over a gun deal and walked. Another guy wanted to actually take a photo of my license. I told him no, happy to show it and my CCW but no way he was getting a pic of either. He insisted and I walked.
There are also still pages on Facebook where guns are bought and sold. Even though FB shut them down a few years ago there are ways around it. Local "Collector Groups" (******* TN GUN COLLECTORS, for example) and other similarly titled pages exist. Pics are posted and pm's are used to negotiate. One cannot use the words "buy, sell, sale, trade, cash" or anything similar. Just a pic and description. Everything else is strictly pm, no public comments other than "sent" meaning you sent an inquiry. The advantage of this method is you can see the other guy's profile and most of the members know each other or know someone who knows them. One guy listed his rifle and said simply, "Wishing it was something else". No FB harm or foul but obviously up for trade.
Gunbrokers is a good site. It does involve shipping and FFL transfers thus more fees. It also does not allow one to inspect the weapon before purchase or have much in the way of recourse if there is a defect or unseen damage in the photos. I have used it a few times for new firearms but exercise caution for used ones.
You might also just ask a few friends if they or someone they know is interested in it. That method insures a safety factor in meeting and in knowing a background of the person. I have a circle of friends who regularly buy, sell, and trade with each other. Comes in handy when looking for a particular item, too.
Just a few ways to do what you want to do and be safe and smart about it. Ask for i.d, require a bill of sale, and take back up. Make sure to check the laws where you live to see what is required. Some areas may require an FFL transfer for all sales. And if you don't know the individual you are meeting remember he could be a fed. Make sure the transaction is legal!
Best of luck.
