Agree with flag and keefy. You are not entitled to any upgrades/freebies per the rule book, but you will often score a better room. It definitely help to call ahead and ask nicely. I.e. you want higher floor, bigger room, upgrade to a suite if available, etc. The worst they can do is say no. I also notice that calling during the early afternoon (before check-in time) is better since the daytime manager is on duty. Calling late night/early morning may get someone on the phone that doesn't have authority and little motivation...

I generally book the cheapest room (1 bed), and then call and get upgraded to 2 bed, or sometimes, a suite at HI/HIX hotels. My success rate in USA is fairly good (over 80% ~20-30 rooms per year, more than half of those on award stays).