I have nearly always received my requests (in fact, I can only think of one time I didn't, and that was because that part of the resort was being refurbished at the time), and all I do is note them on the reservation. I try to keep it very simple, such as upper floor or ground floor, close or far from "fill in the blank", etc. The more specific you try to be, the less latitude they have to give you a room they think will please you.
For example, my last trip at VWL, I requested upper floor, lake view. I was on the fifth floor, and the first room at the beginning of the long hall facing the lake, so I felt like I got what I asked for. But by keeping it simple, they could have really put me anywhere on the 4th or 5th floor on that side of the building and I would have been happy.
If there is anything that is a deal breaker (for example, when I travel with Mom, she won't ride elevators, so I always request ground floor) make that your first request. Then be sure to mention that specific request at the front desk when you start the check in process (so they know to look for that particular type room). Sometimes they don't know why a particular request is being made.
And most important, remember that unless it's a specific booking category, it's just a request, and if there aren't any rooms of that type left, they can't create one. This is especially important when requesting connecting rooms. If only 5 sets of connecting rooms will be available for check in today, and 7 families requested them, there are going to be two disapointed families. If you don't get your request the first night, be sure to ask at check in if you can be moved the next day.