By Your Side
While floating, try resting your hands by your sides, either touching the sides of your body or floating nearby.

On Your Stomach
You can place your hands on your stomach.  You can either keep both hands on your stomach while your fingertips are touching, or sit one hand on top of the other

Behind Your Head
Rest your neck and head by placing your arms upward, keeping your hands underneath your head for support.  Let your head fall into your arms, which will be supported by the buoyant water

Behind Your Back
Join your hands behind your back near your buttocks, either keeping your palms open, facing and touching each other, or by interlocking your fingers.  Stretch by pulling your shoulders back.

Outstretched To Your Sides
This technique is recommended at the beginning of your float to align yourself in the centre of the tank, but it can also be used throughout your experience. 

Try stretching your arms directly above your head.