Over the last year to year and a half I feel like I improved body tension a lot. Here are some things I did that I found to be really useful. YMMV:
1) On all your warm-ups use the worst feet you can possibly find. Just use the hand holds on the problem and try and find jibs, smears etc on other problems and use those. If your feet cut do the problem over.
2) Rooting drills from Power Company
3) Find a steeper wall with a lot of hold density and preferably lots of smaller footholds to choose from. Pick out some jugs or handholds that will never be a limiting factor. Make up some problems where the movement is somewhat complex and it is difficult to keep your feet on. You only complete the boulder when you can do it w/o your feet cutting.
This drill helps advance the rooting drills since it will really teach you the power of position. Once you learn how to physically create tension in your body the next step is understanding where to position yourself in space. Often times on more complex movement the only thing that allows you to keep your feet on is the position of your COG. As the holds get worse and movement becomes harder this becomes increasingly important.
Notice how good climbers COG rarely moves unexpectedly. They are very good at moving themselves into the best positions before they move their hands. If your COG ever moves unexpectedly you were probably out of position and could have moved yourself to a better place before movement was initiated.
I always like watching this video of Jimmy Webb on Warpath. You can really see the tension at the end of some of the moves and how well he is able to set himself up for the next move.
https://www.youtube.com/watch?v=7VCXhkUbIRE
4) Climbing on steep boards like the Moonboard or Tension board. Moonboard climbing is known as being jumpy. Even if you are able to just jump to the next hold try and do the problem without letting your feet cut. We just got the complete 2017 masters set on the Moonboard at my gym. Post some climbs on that thing and I will try them out and see if we do them any differently.