Hmm... Lets see, when you take a reflective reading, you must decide which zone you want that reading to be in, and set as necessary. You may want to take several readings and average then to get shadows and highlites to both be included as much as possible. You can also take readings of thnge that are similar in reflectance to a gray card and use that setting.
When you take an incident reading, you stand in front of the subject and point the light dome toward the camera lens, and thats the setting you will use. If it isn't convenient to do that, place the meter in approximatly same lighting and take a reading. If your main subject is in shadow, creat a shadow that resembles the one surrounding subject and take the reading. It really doesn't get any easier than that.
Anyway, thats how I do it.