A good rule of thumb when drawing from life is to work general to specific. First block out loose shapes of what you are drawing (keep proportions in mind) then slowly build up detail. Make sure to start off drawing lightly so your initial sketch is less visible.
If the objects are in motion, try to concentrate on their gesture. Gesture drawings should be done quickly and loosely (usually only a few minutes at most). Concentrate on the most defining aspects of a pose in that moment and use lines to define it. Try your best to get the whole figure or object drawn withi the time limit. These are a helpful exercise to help train your pace, memory, and the coordination between your mind and hand :•)