All you need to do is don't OLCI until you see a room number assigned. If you did not pick a room but have a specific room number, that is usually the FD doing it for you.

You may see an upgrade there, even though it won't show as one.

That is all I do, seems to work well. 99% of my stays are business trips and in all honesty, it doesn't matter. Doesn't seem worth stressing about