As for Pennies, there are many key dates to look for as well as numerous errors to look for if you have the patience. The obvious things to keep out are the pre 82 pennies as they are 95% copper making them nearly 3 cents each in melt value. I would recommend getting a copy of the Redbook as this will give you a complete list of all coins and great info. As far as the nickels go, I am guessing you already know the 42-45 war nickels were 35% silver, but on the 42s, make sure you see the mint mark above the dome - they are also made lots of 42's on the copper/nickel; there will be no mint mark above the dome on these.
Again, get a copy of Redbook and you will have all the information you could ever ask for.
Good luck!!