What Modern Coins Should I Be Looking For?

That's not what I was asking..i was looking for key dates on modern coins..Jefferson's , Washington's, Lincoln's..stuff like that..
But thanks anyways...

In wpd7's defense, that's how I read your initial question.
A simple list of key dates is a quick search of "key date Lincoln Cent" etc, but if you are just looking for key dates on modern coins you miss out on a lot of coins you "should be on the lookout for".

Jefferson nickel Key dates
1938-D, 1938-S, 1939-D, 1939-S, 1950-D, 1950, 1951 S

For Lincoln cents you have to go back to wheats for any key dates. Memorials don't have any difficult or pricey dates yet (except varieties and errors but that's not what you were asking).
1909S VDB, 1909S, 1914D, 1922P, 1924D, 1931S,

Because of the large amount of information available for each coin denomination when it comes to collecting, all I aggressively search are nickels and cents.

You should be looking for the rare moderns.

The easiest way to identify which are rare is to start a collection. Now days you can get a lot of help because there are so many modern collectors compared to what there were ten or twenty years ago.

You'll find most moderns are tougher in nice shape. If you find a nice AU 1971-D quarter it should go straight into your collection. As time goes by you'll find coins that appear a little different and you'll have the collection to compare them to. For instance there's a '71-D quarter that has a different reverse and another '71-D quarter with a nice DDR.

As you learn you'll know which are tough and which aren't. At first just save the nicest one of every date you see.

When you pick a specialty you can seek out more specific help. You'll be surprised how fast you can become an advanced collector. In the mean time be sure to set aside anything that seems unusual; you can always spend it later. If you're purchasing coins then keep your purchases small at first as you learn the markets. Be sure to sell a coin once in a while so you know the real value of your coins. You don't want to spend a small fortune on coins and then find you've been paying way too much. There's a natural tendency for beginners to overpay anyway so go slow.