One very common problem is that the hull blows downwind of the rig. If the boat is righted from this position, the force on the sail is likely to capsize the boat on top of the unfortunate person who was on the centreboard. To avoid the problem, ask the crew to hang on to the toe straps to prevent the boat coming upright. Pull just the head of the sail out of the water so that the wind will spin it around to the leeward side. Then right the boat as normal. It is often easier to re-enter the boat over the transom. Once aboard, control the boat, grab the tiller, check the ropes and rudder and prepare to sail off.
Always lower the spinnaker at least partially into the chute/bags before bringing the boat up. You must fully or partially recover the spinnaker or you will almost certainly lose control of the righted boat or damage the spinnaker.
A full inversion can be solved by moving both crew and helm to the back of the leeward hull. The stern should sink, screwing the bows up. Use the righting line to pull the masthead to the surface.