This is the most straightforward rescue, beyond simply righting the boat and pumping it dry.
Approach the upturned kayak and grasp it at the bow end. It is essential that the capsized paddler remains in contact with his own or the rescue kayak at all times during the rescue. If he doesn't, the kayaks may be blown along faster than he can swim.
You first try to drain it on its side. It doesn't drain completely that way, so roll it upside down to finish the job. Lift the inverted kayak across your foredeck, and let the water drain out. Make sure it doesn't take on more water or break apart under the strain.
Right the kayak, slip it back into the water and swing it alongside your boat. Direct the stern of the empty boat towards your bow; the paddler in the water will find it easier to get back in from that direction.
Rest both paddles across both decks and grip the empty kayak at the front of the cockpit with one hand and your deck with the other hand.
Tell your friend to lay back into the water and lift both feet into the cockpit. Pushing up and pulling the two kayaks together below him, he can re-enter. The rescuer will need to steady the other kayak until his spray-deck is secure.
Separating again can sometimes be an awkward manoeuvre, especially with tippy kayaks on choppy water. Instruct your friend to perform a low brace support on the water while you push his kayak firmly past you. The movement lends stability to the paddle brace until the kayaks are far enough apart for normal paddling.