1. Ask for it - It never hurts to ask! Some people, myself included, feel awkward trying to sell upgrades to guests. Broaching the subject of an upgrade yourself might be the only way you'll get one from someone more timid at the front desk.
2. Be nice - This should really be common sense, but if you're nice to me I'm going to be nice to you in return. It doesn't have to be with a tip (but hey an extra $20 in my pocket doesn't hurt!), a simple smile and pleasant conversation goes a long way. If you're rude and unpleasant I'm not going to want you in front of me for longer than necessary which means I won't take the time to make an upgrade happen.
3. Be willing to pay - Unless we're very slow I'm not going to be able to justify comp upgrading you three room levels. Any upgrades we sell at the front desk will be at a discount of what you could have originally purchased that room for, but we are a business. We can usually be flexible, but you also need to be realistic.
4. Know what you want - Do your research and know what you've booked and what you'd ideally like to stay in. Maybe you want a bigger room or one with a view; knowing what you want makes it easier for us to make it happen.
5. Be proactive - This goes along with the previous point, but if you do your research ahead of time and know what you want, give the hotel a call ahead of time and ask. My favorite way to sell an upgrade is when someone calls a day or two before checkin and asks about it. This allows the front desk to do any moving around of inventory needed and lets housekeeping know that upgraded room needs to be ready on checkin day.
What are your tips to getting an upgraded hotel room?