One way to be more likely to get an upgrade is to join the hotel's programs. Once you've attained certain status, you are eligible for upgrades. Also select credit cards will automatically give you preferred status. Here are two examples:
- Continental Airline's Presidential Plus card gives you privileged Gold status with Hyatt
- The Ambassador program with InterContinental's Priority Club program gives you complimentary upgrades if available at select hotels. The program currently costs 150 USD, but check out what you get for that amount of money; it is totally worth it.