DO NOT PAY ANYONE FOR THIS FREE INFORMATION!!! It is readily available in the Help section for free, so WHY pay someone for nothing!

You entered the wrong amount, selected the wrong size. Or...worse yet...you wake up one morning and discover someone has put in a bid on a $3000 car on your account and it closes in 36 hours. What can you do?! 

eBay's first advice is to contact the Seller; but you really don't need the Seller to do anything. So long as there are at least 12 to 24 hours left on the auction, you can take care of it yourself. 

Step 1: Copy down the item number (highlight/right click/copy works just fine)

Step 2: Click the HELP button at the top right of your screen.

Step 3: On the HELP page, type "Retracting Bid" into the search bar and click enter.

Step 4: The first article should say Retracting a Bid. click it!

There's good information on that page, but read it after you take care of your immediate problem. With your head consumed with fixing your mistake, you won't absorb eBay's rather confusing explanations and policies. Just skip the blahblahblah and look in the first paragraph for the link that says "BID RETRACTION FORM."

Step 5: Click it!

On the next page, put in the item number and your reason. Reasons are limited. Just pick the one that's closest to your real reason--usually entered wrong amount. Then click RETRACT BID.

Voila!  You have fixed your mistake and can now go and put in the correct bid.

Now go back to that first page and read the policies. You may not be able to follow all of it, but at least you'll be able to honestly say you read it!

If you don't discover the error until the last 12 hours of the sale, then the Seller does have to cancel the bid for you. It's not hard to do.  Takes about two minutes, so don't let any Seller tell you they cannot do it. They can. They just don't want to.

Happy Bidding!

Tyler.