"Backpacker" - Obviously you need item slots early for your first looting.

"Man Tracker" - You want to avoid contact before you reach your shop. And its nice to have it on the counter :)

Last perk really is up to you but I run "Stealthy" or "Alarm gunner". "Load Dropper" is also a valid pick so you can get your "Trapper" items more easily and snare your counter entrances faster.

Airdrops are not so important in this profession since you don't really have time or func to get the drop. But if you can, use something cheap so you can fill the counter e.g. "Trapper" or "Addict".

edit: Trapper is actually really good with Shopkeeper role because you can easily snare your counter entrances if you have the func.

With your outfit you are trying to give a friendly impression to your customers so they don't kill you. (Not quaranteed)
I use a matching set of Baseball cap and a T-Shirt. (It's also nice to market your sponsors e.g. X-plosive Runs)

To complete your "build" you can change your steam name for the game to gain people's trust.
Its more unlikely for customers to attack you if you have name related to your role.
Proper names for your role:
-Fair Trader
-Shopkeeper
-Merchant

You can use your imagination on this one.
(Also thanks for the tip of adding this section BothersomeBen!)

First you need some items. From the place you spawn, find the closest house, loot it and run to the survival station (or other house with a counter) to set up your shop. By this point if you don't have atleast 5 items in your inventory, craft something to satisfy your customers.

Some basics on how to work as a merchant:
-Mostly stay behind your counter.
-Don't attack anyone.
-You can put up snares on your counter's entrances (Thanks for the tip Tacky!)
-Jumping is usually referred as friendly.
-Communicate with nodding and shaking head.
-You can and should leave your shop to restack your items. With a friend this is a lot easier.
-After the gas hits, you may leave the shop, remember but lock the doors.

What happens if customers really do attack you? (Thanks for the tip BothersomeBen!)
-If you have, use pepperspray or a smoke bomb, take what you can with you and leave. When attacker is gone, go back to your shop. (Personally I think this one has the best outcome)
-Just guard when they attack you. (Sometimes they actually stopped attacking after seeing I that I don't mean harm)
-Or if you definately want, you can fight back and defend your shop.

Leave a comment what happend to you when you tried this!

Ps. Role of a shopkeeper is not my original idea. I've seen people do this in other games and wanted to adapt the idea for the Culling as efficiently as possible.