If you are having a hard time choosing a plan, remember your chess basics. Does your plan develop/improve your pieces? Does your plan control the center? Does your plan give you flexibility while forcing your opponent to do things he doesn't want to do?
In my opening, I have certain plans that allow me to win a pawn. In the middle game, I might be looking for ways to win a piece. Just don't forget, your opponent is planning, too! Watch out for his traps while you make your own.
One last thing - don't be afraid to change your plan! Every move creates a different position - what looked good a move ago might not work anymore. That's why you want to have your pieces in places where you can change it up if you need to.
Best of luck!
I am at the stage of realising that planning is very important during the game, how do I develop this skill of choosing the right plan, are there principles involved that I need to learn