Well it takes a while really it did the same with me I was getting discouraged too. But I never stopped though and it kept me motivated to find something and all at once I found a clipped planchet and 1994 180°rotated die cent ex it takes awhile. I get I get a variety of coins like nickels dimes quarters so you don't have to keep looking at pennies all day.
Please remember if it were that easy to find doubled dies and other errors in circulation, they wouldn't be worth much, because everyone would be able to find them. Just because a coin, or some of it's lettering or design elements are doubled, does not mean it is a doubled die coin - in fact, as shown here numerous times, the rate of finding a true doubled die to the rate of finding ejection or mechanical doubling is very small. One of the best books for Searchers to have, imo, is the CherryPicker's Guide to Die Varieties, which illustrates doubled dies, rpms, etc., and explains the various forms of doubling in the Appendix. (two volumes) There are also excellent websites, usually by denomination, that illustrate doubled dies for that series or denomination. Please don't get frustrated with us when we tell you you coins aren't doubled dies - they either are, or aren't. If they aren't, should we tell you they are, or tell you the truth about them?
I've been trying to document it to teach people .... here's part of the info I'm working on First of all there are 3 primary methods that doubling occurs: (1) Machine made - When a part of the minting machine moves slightly. This can be the die, the stamping arm, etc (2) Usage Wear made - When the die itself starts wearing These first two methods create the “illusion” of doubling. But this is not the doubling that people relate to worth money. (3) Man Mistake (slips quality control) made - When in the process of creating the hubs and die itself, there is movement or rotation thus creating doubling. This is the reason one must understand the entire process as it becomes more obvious when one knows this information. So we have (1) Machine Made (2) Usage Wear Made (3) Man Made Most collectors are after everything that is (3) Man Made, or made during the hub/die making process.
