As a young PL I was told some great advice.  Never say no.  Instead say We can do that but……  For example a new tasking is beyond your capability.  I would say Sir, we can do that but, I have these other taskers and would need relief from one of them to execute this new mission.  This lets the superior decide which tasks you are accomplishing are more important.

I also try to identify events that I can sacrifice in the event of a “jump through my butt” tasking.

Finally, think economy of scale.  What tasks are complimentary.  Can I do one thing that qualifies for two.  For example, leader training and soldier training are nearly identical.  I teach everyone the leader training brief.  This turns 3 hours into 1.  How many supporting tasks are duplicated in the company’s METL?  Can I knock out two METLS in a single event by adding one or two tasks?  Gain efficiency by understanding what the training requires.