Using a proxy requires that you know how to figure out the maximum you are willing to pay for something.  Here are a couple of methods that may help you figure yours out:
 
Method 1:   Close your eyes and imagine that the auction you are thinking about has ended.  Your bid was beat by 5 cents.  Would you be upset?  Do you feel that you would have bid more if you had had enough time?  Then you haven't found your maximum yet!  Imagine making your max bid higher and then imagine THAT bid was beat by 5 cents.  How do you feel now?  Keep doing that until you reach a point where you say to yourself "That's just too much for me, if someone wants to pay that much for it, they can have it".  Then you will have found your Max bid amount.
 
Method 2:  Imagine that eBay has changed their auction format.  Now you are only allowed to bid ONCE per auction.  If you try to bid more than once, eBay simply won't allow it to happen.  You get one chance, and one chance only.  What would you bid in that case?
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