Some cleanings will be obvious, others you won't recognize until you've seen a lot of coins. When something looks "off", trust your gut.
Harsh cleaning has as many different looks as there are ways to do it. That of course is a large part of the problem in identifying harsh cleaning. Can you learn how to identify all of those different looks ? Sure, with lots and lots of experience. But there is something else that is more helpful and actually easier to learn - learn what coins that have not been messed with look like. Yeah it still takes experience, but less of it.
When I started out collecting I had a big problem with this subject. I would buy a coin think its great submit it and find out its been cleaned. For this reason I decided to purchase already graded coins and not take the chance. I spent way to much money on the hopes that a coin would grade out. It is very hard for me anyways to tell if a coin has been cleaned under certain circumstances other times its obvious. Hope my input helps with your decisions.
Spend some time looking at mint state coins in ngc or pcgs holders on ebay. It's free and you can take your time looking. Also look at the details graded coins so you can see what is not market acceptable and troublesome. Also read a few books on coin collecting.
