Float-bags are essential in any kayak lacking watertight bow and stern compartments. Belt-and-suspenders types will even put float-bags behind watertight bulkheads. Ideally, every corner of your boat not claimed by gear (and you should pack as much of this in waterproof bags as you can) or given over to your own good self should be filled with float-bags. When you capsize and make a wet exit—it's when and not if, I'm afraid, however skillful you may be—you'll be glad you took the trouble. Not only will your kayak stay on the surface, but you'll find that the extra flotation makes the difficult job of bailing out a swamped boat much easier.

A stern painter ("tow-line") and a perimeter grab-line will facilitate rescue and recovery, too, as well as helping in other hard chances. Test both before you need them!
Luckily, emergencies don't happen every day. But you'll find a use for your deck tie-downs on each trip. You won't need to keep a harpoon handy, but you'll want to consult a map now and again. No problem. Just put your maps and charts in a waterproof envelope with a transparent window, and then tuck it where you can see it as you paddle. (A short safety lanyard connecting map-case and kayak is a good idea.) You'll also want a spare paddle, of course. It can go under the tie-downs on the stern deck. And that's only the beginning. You'll find new uses for your deck tie-downs every time you go out. Just don't pile your gear too high. Deck cargo adds wind-resistance and makes rescues more difficult.

Will you need a rudder?
That depends on your kayak—and on you. A rudder is no substitute for paddling skill, nor is it primarily for steering your boat. Still, many kayaks show a pronounced tendency to "weathercock," or turn into the wind, particularly when paddled in strong cross-winds. A rudder can make such boats much more manageable. Long trips will therefore be much less tiring, and you'll be safer. There's a downside to rudders, however. They're often worse than useless on fast-moving rivers, they add unavoidable complexity, and they're vulnerable to damage. The best advice? Learn to control your boat in protected waters before you go shopping for a rudder, and then try before you buy, in as wide a range of conditions as possible.

Once you start thinking about trips that take you over the horizon, you'll want a desk-mounted compass, and you'd be wise to consider an integral bilge pump, too. All kayaks ship small amounts of water when they're under way. No hatch or spray skirt is absolutely watertight, and rudder fittings always leak. If your plans include extended open-water crossings, you'll be glad that you can pump out bilge water before it affects your boat's handling qualities—and without removing your spray skirt. Think of a bilge pump as a flood insurance policy. You won't need it often, but when you do need it, you'll really need it!

That's enough to get you started.
You'll probably have your own additions to the list, but this is part of the fun. A kayak's the best type of personal watercraft, after all. Just don't get carried away. Put safety first and comfort and convenience second, and leave the clutter at home. Paddle a clean machine. 'Nuff said.