First, you must decide what type of ad you want to place.  The three types are:

1. Auction - With an auction, you must set the starting price and the bid increment and you may set a buy-it price (the price at which you are willing to sell early at) and a reserve price (a price below which you are not required to sell).
2. Classified - When you post a classified ad, you set a purchase price... the price at which you will sell the item at.  People have the option to buy immediately at the set price only.
3. Wanted - Upon placing a wanted ad, you set the maximum price you are willing to pay for an item.  People can contact you through email to arrange the details.

Once you know which type of ad you would like, get all your information together.  You will need the following:

1. A clear, concise title for the item.  Only put information here that would effect whether or not someone would want to look at the item. Selling points should go in the description.  Eg: 'NEW 18k Gold rng. 2 ct Rnd & 2 .25 ct. prncs. cut' is more likely to confuse than entice... a better example would be 'Stunning 18k engagement ring - 2.5 carats total' - the second is shorter, clearer and easier to read than the first.
2. The category to place the item in.
3. An image of the item is not required, but it is recommended.  Many people are hesitant to e-mail for more details about an item and an image answers most questions about an item.  Unlike other auction sites, you do not need to set up separate web hosting for your image.  Just have it on your computer where you can find it, and you can upload it at the same time you submit your auction information.  Because classAbid is hosting your image for you, you must keep the file size under 50K.  If you save your image as a jpeg, you should be able to fit a 640x480 photograph into that size.
4. Decide on the length of time you want your auction to run for.  The longer the time, the more likely people will notice the item.  However, keep in mind that people often don't want to wait two months to find out if their bid wins - the more expensive the item, the less likely people are to bid early.  Eg: it's easy to know you'll be able to buy that pair of garnet earrings for the $27 you bid, but you can't be sure that you'll be able to afford that two year old mustang convertible for $19,000 two months from now.
5. Available shipping methods.  How are you willing to get the item to the customer?  If you want to specify more than one, list them all in the description.
6. What type of payment will you accept?  You can specify multiple type of payment here and any that are not listed can be included in the description (e.g. financing available)
7. A full description of the item listing including size, colour, condition and any other information you have.  The more information you have here, the more likely you are to sell.  Try and keep the description readable - you have lots of space.  If you want, you can include HTML tags in the description eg <b>...</b> around text will make it bold
8. If you're not logged in, you will have to enter your alias and password.  If you don't have one, just register it's easy and free.
9. The starting price, buy-it price, reserve price, bid increment, and maximum price as applicable.

Once you have all this together, got to the Post New Auction, Post New Classified, or Post New Wanted Ad page and enter all the information.  To upload your image (if you have one) click on the browse link and find the image on your computer.  When you've got it all filled out, click on the preview button and you will be taken to the confirmation page.  If you are uploading an image, this is when it is sent to the server.  So it may take a couple of minutes for the next page to come up.  DOUBLE CHECK your entry.  This is the place to catch any spelling or grammar errors.  Once you're sure that everything is how you want it, click the Post Item button to make your ad final.

You're done!