Also, the opening lead decision for a given contract and auction can vary depending on whether one is playing IMPs or matchpoints. Because it is the least informed action of the hand, one should take care in matchpoints to not give away the hand with the lead. Leading "with the field" is often advocated, on the premise that in most hands one gets another chance to at least obtain an average.
Alternatively in IMPs more aggressive leads are less risky, and employed by experts more often. The loss od an overtrick is inconsequential if any measurable chance of setting the contract ensues.
As always, visualization of the opponent hands is paramount in making good lead choices. Understanding whether the opponents have stretched to the current contract, or failed to investigate higher, can assist one in evaluating the appropriate level of risk for a given lead situation.