One way to get an upgrade in a hotel where you have no "pull", eg: no frequent guest status, is to ask for a corner room. Corner rooms are almost always bigger and nicer, many times with windows on 2 sides, so even if it's not an upgrade per se, it'll likely be better than a standard room. Also, don't try to check in at 10 am - not enough rooms ready - or 6 pm - too many people arriving. The best time to get to a hotel is about 3 or 4 pm, as all the rooms are cleaned by then but they have not yet done all the pre-assignments.