I met with my trainer at Equinox yesterday for a little ass whopping. Actually it's my quads and abs feeling the pain today — thanks, Lauren! But I did learn a new tip from trainer Lauren while doing a standing cable twist (hence the pain in my abs), and I'm going to share it with you.
When doing an exercise that works your body halves separately, like lunges or side planks, do your reps on the weaker side first. Even though the sides of your body are moving independently, both sides of your body are still working. You want to give your weaker side a chance to perform reps cleanly with good technique before tiring out. Generally, the leg you don't want to lunge on is your weaker leg. Don't avoid it! Start with it.