Instead of just smashing the bag without a plan - put a basic routine together.
I took KK'h "heavy bag" routine above in the stickies & used it as a basis for my own beginner routine. 3mins work, 30s rest & repeat, starting light & getting gradually heavier. I start with at least 1 min of jabs, then 1 min jab + cross, then 1 min jab+cross+hook.
Then I rest & do another 3 min of someting else - although I later may come back & re-do some of the previous sets at full-power.
As my "striking" interest is MT, I also include some sets with kicks, and I finish with a few "freestyle" sets where just try to throw whatever in.
You find the previous drills make your "freestyle" sets technically better (or at least, they FEEL that way to me...)