I was always from the school of pumping up the "looker" muscles
The groups that will give first impressions to the judges i.e.biceps,delts/front delts,and pecs.
Of course if you have something lagging then give that group the priority
Depending on the pump up room...size,equipment,competitors...I think there's something to be said for just posing for 5-10 minutes.
Remember all those practice sessions you've been doing?
I got some great pumps from posing...
Another thing to consider depending on your experience is that you can at least get a pump!
I've ran that road in some shows....your so wiped out and you've been so carb depleted for weeks ,
plus your probably dehydrated,that you can't get a pump.
Its a delicate balance.
The carb game is another chapter though...
Best of luck