1) Check-in later (at least after 2:00). The closer to the evening the better chance the front desk will know which rooms are available/booked.
2) Make sure to mention special occasions (birthdays, anniversaries, etc.). Call ahead to make this request.
3) Become a regular...if you travel to the same place often, stay in the same hotel. You will become known and they will want to reward your loyalty.
4) Do not ask with other guests around...the front desk will not want to start a chain reaction.
5) Join a hotel rewards program. There are many perks, including a possible upgrade.
6) Be nice! Front desk clerks are used to rude and demanding customers. Your chances are much greater if you ask with a smile!
7) If you really want to secure your upgrade chances, TIP. No more than $20 is necessary. Yes...money talks!