Meters and ISO settings provide at best a starting point, since meters vary on their sensitivity to infrared. Exposure on a sunny day with a red filter in place should come out about 1/125 at f11, which is about 50 ISO; about 1-2 stops more for an opaque filter (25-12 ISO). This is for an external meter. If you have a through the lens meter in your camera, I recommend you put the filter in place and meter a sunny day scene. Then adjust the ISO until you get 1/125 at f11. That should give you a good starting point. This is probably what jordi is referring to with ISO 200. I've found on my M6TTL that 400 is about right with a B+W 093 (opaque) filter in place, for example. It all depends on how sensitive the in camera meter is to infrared. Whatever way you meter, you need to bracket and experiment a bit. With HIE, you will get the best effects in good sunlight. Clouds seem to reduce infrared more than they do visible light, so in cloudy conditions, you will need to open up a bit more, and the infrared effect will be less. So to get the most infrared impact from your images, you will want to be shooting in bright sunlight, anyway. There's a lot of good info at:
You can also sign up there for the infrared digest. Good shooting and good luck.