Tracking SAC Its definitely important for new divers or if doing deco diving and planning. SAC is impacted by Depth, Water temp, Current and Visibility.
Depth - You suck down more gas the deeper you go. In addition deep dives can be more stressful which can result in added air use. Keep a close eye on the SPG when going deep. Below 100', pay attention as narcosis kicks in. If you realize your sucking down air and you are deep get shallower. This is not always possible, but even 10' will make a difference.
Cold - There are so many things that make cold water diving more difficult, cumbersome exposure suits, more weight, hoods, and thick gloves all make the diving more challenging. Its normal to use more air in cold water even for an experienced diver.
Current - current is not an issue unless you have to exit at the same spot you entered. I always swim into the current at the start of the dive when possible. If your planning a dive in current swim into the current for 75% of your planned time or more. Its amazing how much ground you cover swimming with the current. Do not swim past your exit point.
Visibility - Low vis makes things harder especially if you don't dive in low vis much. Harder = higher SAC. We were in the FL keys, the weather was awesome, but the vis was less than 10' after a storm. Eight people on the boat, four never made it to the reef. Two sat out the dive, and two guys spend time in water were 10' vis is considered good! Unfortunately poor vis takes practice and means more stress.
Realize any event that is stressful UW will general result in a higher SAC rate. This is compounded by depth.