In 1992 the mints started using a new varirty of reverse on the cent but through 1998 some of the old reverse were used. Here is a list of WAM and CAM that can be found.
1. 1992 Close AM - extremely rare
2. 1998 S Close AM
3. 1992 D Close AM
4. 1999 S Close AM
5. 1999 Wide AM
6. 1998 Wide AM
7. 2000 Wide AM - least rare
Now there is also a 1996 WAM that has been reported but I have not seen it.
Their are two good ways to distinguish the Wide AM reverse from the Close AM reverse:
1) Obviously, if there is a space between the A and M in AMERICA you are looking at a "Wide AM".
If it appears the A and M are practically touching, you are looking at a "Close AM"
2) The Initials FG on the reverse are further from the memorial than on the "Close AM" reverse.
I hope this helps. You can also go here:
http://www.lincolncentresource.com/wideams.html