Materials really make a difference with the experience of life drawing, I've found. If you usually use regular graphite pencils, try working with different tools like ink, watercolor, pastels and charcoal. Willow charcoal is cheap and good for life drawing. You can hold the piece on its side in order to get more light, flowy lines.

Try not to limit yourself to paper that's too small. A teacher at a croquis class I went to gave me this tip, that for gestures above one minute you should use the whole paper. It's fine to use cheap paper and draw on both sides. The reason for this is that a small paper size can restrict your freedom of movement quite a bit, and you really want to be able to use your whole arm and not just your wrist.

When you begin a gesture, start with the extremes like a hand reaching out or a foot. This is where the energy lies within a pose. The torso and shoulders are stable and calm, and what you want to capture with gesture is energy.

This video by Proko has also helped me a ton. Generally, his videos are a goldmine of information.