I usually call the property ahead of time, appropriate to the place and season. If you know a lot of rooms in the town/city/resort are booked months out, call early...then follow up a day before. I ask to speak to whomever handles reservations and rooms on site...this could be the front desk mgr. or maybe even someone in sales that you get turned over to. I say I'm calling about my upcoming stay and of course I know that nothing can be guaranteed, but since I've booked a room at such a low rate, I would like to know what that entitles me to since I am ****. They will very often become involved at that point, even discussing the type of room you would like and, if you're lucky, blocking it. On a few occasions I've actually been told the room was blocked for me. Once, another high end chain faxed me a floor plan so that I could choose. But that has only happened once and I don't expect to see it again. After the first call a follow up is necessary even if you think all is perfect. I have had some lovely rooms and occasionally suites with this combination of calls informing them of my wishes. Have a great trip!

I don't call. But I do use the virtual concierge sometimes.
For best result - First show my elite card. If I was not offered an upgrade when I was handed the key, I would ask very politely and never sound demanding. It worked most of the time. When failed, there's always a reasonable explanation.