This may seem obvious and unnecessary, but you'd be surprised at the people who don't yet know how to make a proper auction. There is no exact way to make an auction, but there are a few necessary steps in order to host an effective one. In any auction, you will want have these components.
TITLE THE AUCTION - Duh. Put the name of your item. For example, "Auctioning Vindicator Minigun".
DESCRIPTION - Here you will write a little bit about the item you are auctioning. For example, "The Vindicator is 100/100 condition, and comes with 200 free ammo" It's also a good idea to add images of your item, but this is optional of course.
STARTING BID - This is how much caps/items you want the bidding to begin at.
Examples of Starting Bids,
Starting Bid: 200,000 Caps - If you prefer a caps only auction
or
Starting Bid: 20 Pancor Jackhammer - If you prefer a items only auction
Or you can have
Starting Bid: 100,000 Caps AND 10 Pancor Jackhammers - If you want a mixed auction
MINIMUM RAISE - The minimum raise is pretty self explanatory; it's the lowest bid a player can place above the current bid. Usually, it is a good idea to keep your minimum raise price at about 10% of your starting bid value. This can be in caps or items; whichever you allow.
Examples of Minimum Raises,
Minimum Raise: 20,000 Caps
or
Minimum Raise: 2 Pancor Jackhammers
or
Minimum Raise: 10,000 caps and 1 Pancor Jackhammer
AUCTION END TIME - This is simply how long you want the auction to last. An average auction lasts anywhere from 24-48 hours. Often times, someone will try to do last minute bids to "snipe" the auction. Since this is unfair, some people will extend the auction for another hour after each bid past the announced end time.
For example, someone places a bid with only 10 minutes left of your auction. This isn't fair to other bidders who may not be online at the time. So when this happens, you could announce that the auction will go on for another hour.
(OPTIONAL) BUYOUT PRICE - This is a set amount that would instantly buyout the auction. It's normally set much higher than the items actual value, just in case someone really needs the item you are auctioning. For example, an item is worth about 100,000 caps in direct trade so you would set the buyout price at something like 350,000. Most people don't even bother with buyouts, but they are a fun option.
Now I will give you an example auction.
Title - AUCTIONING A UNIQUE GATLING LASER
Description - This Gatling Laser is brand new, 100/100. It is +25% Minimum Dmg, +25% Maximum Dmg, +Action Point, +5 Range, and +5 Crit Chance.
Starting Bid - Starting Bid - 80,000 Caps
Minimum Raise - Minimum Raise - 8,000 Caps
Buyout - Buyout - 300,000 Caps
End Time - Auction ends in 24 hours, or 1 hour after the last bid in the allotted time.
One more note, make sure you have some basic idea of an items value, or you will over-price and scare away potential bidders. Or worse, you could under-price and sell the item for much less than it's worth. To find rough player-values of items, browse through the Barter Grounds sub-section, and find some old auctions or "want to sell/want to buy" posts. This should give you an idea where to base the prices in your auction.
I Hope this guide will help you make more effective auctions, and I'm sure it will help you to avoid trolling and flaming in the Barter Grounds. Good luck, and happy auctioning!