A drop or two of love juice (synthetic oil only) in the airline at the bottom of the minireg, gas up and fire a dozen or so shots off to circulate the oil through the system.
Keep it clean, especially the trigger pivot point.
Check the seal underneath the breach, as this is a weak point, and can be lost easily. i've seen them glued in, but be careful to keep the top of the seal clean.
Keep the bolt clean.
Each has his or her own priority for maintenance, but these should keep it singing.