The 1918-D is a common date in the Lincoln Cent series, though its mintage is well below that of the ultra-common dates such as the 1918-P. Collectors may choose between Brown, Red-Brown, and Red examples, of which there is a sufficient supply to meet most demand. The key aspect of this date is the strike quality. At Denver, dies were used even after they became worn, thus many 1918-D Cents have mushy details or surface granularity. When seeking out a 1918-D Cent, look for examples with a crisp strike and hard, lustrous surfaces. As with all Lincoln Cents (and copper coins in general), shy away from overly spotted examples or those with unattractive toning.
Full Red 1918-D Cents are scarce, and are most likely to be seen in MS64. In MS65, this date is quite rare and, in MS66RD and above, the 1918-D Cent is downright rare. The finest example certified by PCGS is a single MS67RD.