There have been several posts advising against requesting a change in flight level during flight, as this seems to mess up ATC and results in no descent instructions from cruise altitude. Unfortunately, stuff happens. Towards the end of a Narita-KSFO flight I accidentally hit the key to request an altitude change due to clouds. After uttering a few expletives, I decided to try to salvage the flight by getting down to center handoff altitude. I requested and received clearance to FL210, then 12 thousand. As I descended below center altitude (14,500 in my case), I was handed off to approach and the rest of the flight proceeded normally, with descent instructions and vectors to the ILS. So, if you do happen to request a change in flight level during flight and find yourself without descent instructions, get down to handoff altitude a reasonable distance from the airport and approach should be able to pick it up from there.