I'm always covering things to do on this blog, I rarely cover things you shouldn't do. I have to give lots of credit to everyone on Twitter who helped me compile this list. Most of these are obvious and hopefully none of my wonderful readers do these but there are some people who still do.

1: Lousy photo. Blurry, dark, yellow tinged, bad background, etc. these photos don't give customers a good impression aboNothing telut your products.
2: Ignore emails. Nothing tells customers you don't care than not acknowledging their emails.
3: Lacking descriptions. How is a customer supposed to know they won't have an allergic reaction to your soap without ingredients or that a shirt will fit without the size?
4: Shipping is more than the cost of the item or extremely high. Find a cheaper shipping option or adjust your prices to balance them out.
5: Poor spelling and grammar. One or two mistakes, especially if very common ones like it's and its, isnt going to be a big problem. Howevar if ur listing make no cents, you has a problm.
6: Don't offer Paypal. Yes, I know it's owned by eBay and therefore evil in many eyes but it is the biggest player in taking payments online so you need to offer it.
7: Smoke around your products or let your pets around fabric/fiber goods. Nothing will cause someone to never buy from you again more than an allergic reaction or icky smell. If you want repeat customers smoke outside and banish the pets from your workspace.
8: Underpricing yourself. This is very common and I know it sounds counterintuitive but it's true. Prices that are too low imply cheap construction and materials. If your products are high quality you shoudl be pricing them accordingly.
9: Outrageous prices. Okay, so in the are of handmade products underpricing is a far more common problem but you can overprice your work as well. $300 is perfectly reasonable for an original painting (depending on size & skill maybe too low) but not for a print no matter how high quality is it.
10: Don't fill out your profile and location. Would you want to buy from someone who's anonymous?
11: Threaten your customers. Don't fill your policies with threats and don'ts, keep things positive but firm. For example "Items are shipped as soon as payment clears" is much better than "If your check bounces you don't get your item".
12: Unclear policies. If you only ship on Mondays, Wednesday, and Fridays you needs to state this. Be simple and straightforward.
13: Don't organize your shop. 100 items with no sections/categories is hard to navigate when looking for something specific.
14: Make a bad quality product. Strange, unusual, creepy, even ugly (chinese crested dogs?) all sell great if you can find your market, but bad doesn't sell.