This is shown schematically below and the gamma position is marked above in the example for hexane. The nitrile carbon is significantly shielding and adjacent carbons tend to occur in the 20 - 25 region. Alkene carbons tend to have chemical shifts in the range 110 - 140, as shown in the examples below. Conjugation between alkene centers has little effect, as demonstrated by the two middle structures shown below. Conjugation with an oxygen, however, has a dramatic shielding effect, which is attributed to contributions from the resonance forms shown below.
Carbonyls are the most highly deshielded carbons which are typically encountered.
Typical chemical shifts occur in the region 170 - 210 with esters, carboxylic acids and amides at the low end, and simple ketones and aldehydes at the high end of the range. Aromatic carbons have chemical shifts in the range 120 - 140 and are shifted within this range by the nature of the attached substituent. The multiplicity of aromatic peaks in the non-decoupled spectrum is useful for identifying aromatic substitution patterns.