How Hard Is It To Find Errors?

None of the coins you listed are errors, they are die varieties. If that is what you are looking for, you may want to try looking for RPMs(repunched mint marks) as well but there are many more doubled dies that you did not list. You will probably want to get a Lincoln series book or CherryPickers' Guide Vol 1 and also check out the varieties by year and mint mark at http://www.coppercoins.com/.

If you are looking for errors, most of them are pretty obvious and readily stick out but can be difficult to find and many will not fit in a roll. Also, errors since 2000 are incredibly difficult to find since the Mint has implemented some new procedures for reducing the release of errors(riddling machines to remove wrong sized coins, not shipping bags anymore, etc). Incomplete planchets(clips), off center, Cud, broadstrike, double strike, off metal, brockage, etc are all errors. If you are wanting to learn more about them, I suggest this book.

If finding something of value in change was so easy, everyone would be doing it

I don't roll search, but the wife & I throw change in a bowl that I go through before we spend it. I'd guess I look at a few hundred dollars every year. From where I sit you are doing pretty good. I haven't found any of the ones you have listed, although I have found a couple dollars face value of silver over the last few years.

probobly the easiest errors to find are Struck Through Grease, and misaligned dies. They bring little premiums compaired to other errors because they are so common. I suggest nickels if you are looking for other types of errors, die breaks of all sizes are much easier to find in nickels because the metal is harder and therefore dies wear and break more easily. Clipped planchets and other errors are also comparitavely common in nickels.

I have searched over $900 worth of pennies and have not found a 1970s small date or for that matter a 1960 small date(I see plenty of 60 d small dates)and have never found a 1909 wheat or an Indian Head cent. My best find is a 1982 s proof cent. I think you have been very fortunate with your finds so far.

My kids and I just went through $50 worth of pennies and found NO Wide AM's. That is what I was hoping for. Found plenty of 82 and 82D small dates both varieties; 15 wheats in the 40's and 50's; 6 canadians, 1 blank planchet; 1-2002 very weak obv; a 1969 with GRANT TAKES RICHMOND engraved on obv in a shadow box with an arrow pointing to Lincoln's mouth, cartoon like; 1- 199? that takes 10X to read is it so weak with a nice reverse; lastly a 1995 with the planform of an apple punched out. Probably compliments of a phone manufacturer. My son was able to nearly complete his LMC's. So it was pretty good afterall but the Wide AM's have me baffled.

it depends on what kind of error coin you're looking for
coins Struck Through Grease are easy to find in almost every roll. die cracks can be found on many coins.
i guess you can call these errors but they arent really too desirable to most collectors.
errors like unstruck planchets or offcenter strikes are most desirable but less likely to find

Yeah a 1999 Wide AM is one of my goals. Any double die would be nice too.