Is there anything you can do to make the downwind groove easier to find?
The more open leeched your spinnaker is, the narrower the steering envelope becomes. In other words, the flatter the spinnaker, the tougher it is to fly and the more attention it requires from both the trimmer and the helmsman. It's like having a fine-entry jib when you're sailing upwind-the difference in steering between being light and heavy is not very great. One way to make the spinnaker a little more forgiving is to give it a rounder shape by closing the leeches a little. On a broad reach or run, choke it down by lowering the pole and moving the sheet lead forward. This will give you more of a curl and open the steering groove up a little.

Another way to make steering a little easier is to sail on the fast (high) side when you are trying to pick your optimum VMG downwind. It's similar to widening the upwind groove by sailing a little on the full side when you're beating. Most people err on the slow side downwind, and this is a mistake. You will pay for being low much more than you will pay for being high, because once you start to slow down the problem accumulates, and it will take you longer to get back up to full speed.

What can you use as steering guides downwind?
I like to use everything possible as a steering reference. If you have a stern light ahead that's on a boat steering same the course you are, nothing's better to keep you going straight. It's the same when you can see a lighthouse or mark that you're headed to. Sometimes you can line up a star in your shroud, but remember that this will only work short periods of time. The angle of waves will also help you a lot at night. Another helpful guide is sail trim. If your sails are trimmed for the course you want to steer and all of a sudden they start luffing, then either you've been headed or you're steering high of course. So I'd say you should look at wind angle, waves, stars, moon, close stern lights, angle of the sails, feel of the wind on your face, angle of heel, horizon, a point on land-a whole bunch of things. You have to remember current leeway and all the things that are going to affect the course you're steering. The best way to steer a straight course for a mark (if you can see it) is to line up the mark with something on land behind and then hold that bearing constant.

Do you have any tricks for steering on an overpowered reach?
Making sure you have good leverage on the wheel or tiller and communicating with the crew are key. Too many helmsmen just sit there with the tiller up under their neck and don't say anything. You have to let the sailtrimmers know how the helm is. Make sure that they ease as much a possible, and don't ever overtrim when you're in overpowering conditions. The spinnaker is particularly easy to over trim because it looks so pretty when it's in tight. You'll find that the better crew tend to lose their spinnaker more often than you might think because it's eased so much. I like to use telltales near the spinnaker leeches to help make sure that the sail is always eased to the maximum. The mainsail trimmer is equally important as the spinnaker trimmer, and he's usually right next to the helmsman, so there should be a lot of talking back and forth. Make sure somebody constantly monitors the vang as well.

It's usually worth going with the spinnaker even if it means you round up every once in a while. This may make it harder to steer than if you had a genoa but it's faster. Don't start depowering the rig until you're at the point where you can't steer the boat straight (because of weather helm) and the rudder begins to stall. The main rule for depowering is to start at the back of the sail plan and proceed forward. The first thing to do, assuming that the spinnaker is eased as much as possible, is to ease the mainsheet and the vang. Other ways to depowering the main, and therefore reducing helm, are bending the mast, pulling in the flattener, or even going to a reef. Secondly, you should take a staysail down, if you're flying it, to reduce heel and therefore lessen weather helm. Finally, you can go to a flatter spinnaker. The helmsman is the only person who can really feel when it is time to make these changes.

When weather helm builds up and the rudder begins to stall (i.e. there's bubble of air around it) before you can depower enough, one technique for reattaching flow on the rudder is to give the helm a few quick pumps. Keep an eye out for waves as well because they can tip the boat over, lifting much of the rudder out of the water. Anticipate big waves by steering a little lower so they won't push you over so much. As usual, steer higher in the relative lulls and lower in the puffs.

How about when you get out of control on a run?
One thing I tell helmsmen when they're steering downwind in severe conditions is that it's very much like skiing. On skis you have to keep you body, and therefore your center of effort over the skis. You can't lean way uphill or way downhill. In sailing, you have to keep your whole sailplan over the hull. Looking at it another way, you have to steer so you keep the hull under the sailplan and prevent the keel from becoming a pendulum. For example, if the boat heels to the right, then steer under it to the right. If the boat heels to the left, steer under it that way. These steering corrections should be fairly small; you don't want to over steer and cause a turn the other way. If you're having a hard time keeping the boat under the sails, perhaps your crew weight is too much to one side. You definitely want to balance the helm in these conditions.

A helmsman can have problems steering downwind because most boats have too much sail in a breeze and can't be as effectively reefed as they can be upwind. Even if you could reef the main you'd end up with too much sail on the spinnaker side. So it's critical to figure out a way to balance the boat with the sails (as it is on any other point of sail) and this requires working extra hard with the sailtrimmers. For example, if the boat wants to round up to windward, ask the person on the guy to square the pole. If the boat wants to go out to leeward, ask for the pole to be eased forward and the sheet trimmed.