Disclaimer: This is just a guide to give you an idea of what your coin might grade. Often coins will grade higher on one side vs. the other. In example, it's possible for a coin to grade G4 on its obverse, but grade VG8 on its reverse. Also, this guide is not a claim that one's coin will obtain any grade listed if submitted to a third party grading service.
Along with a grade, Lincoln Cent also come with three other designations, BN (Brown), RB (Red-Brown), RD (Full Red) with the R being the most desirable state of preservation for normally toned cents. Below are examples of each state of toning.
A Lincoln Cent is difficult to grade, but one aspect of grading the MS grades is in the smallest of details. Many cents appear mark free in the fields, but a few places that's often over looked is the high points of the hair, beard and the lower shoulder. Sometimes these marks can't be easily seen without a 5x jeweler's loupe, so when grading Lincoln Cent, pay close attention to these areas.