Sail in more wind unless you're on the extreme long tack on a shifty day, and you know that, if you sail straight, you will get a massive shift to tack or jibe on. A 20- or 30-degree shift will give you a bigger gain than a little more wind. In tough tactical situations like this, you have to make a judgment call on what will give you the biggest gain. For example, sailing in slightly more wind will give you a two-length gain on those you tacked away from (in the absence of a shift), but getting a 20-degree shift that your competitor missed will give you an eight-length gain. In this situation, go for the shift.