A few bits of advice:
* If the nearest airport to your house is a hub for any particular airline, you may want to look at their credit card first. This will give you more opportunities to use your miles on more direct flights to more places, plus the flights you pay for in the future are more likely to be on that airline. Most airlines have limited availability for award tickets on their flights, so even if you can't use the miles for your upcoming funeral you may be able to book your next vacation when you're able to snatch the award tickets early.
* If you don't travel often, it probably doesn't pay to sign up for more than one or two mileage programs. Most airlines expire your mileage account after 18-24 months if you don't earn or use any miles during that time. There are a few pretty cheap ways to drag this out. e-miles.com, e-rewards.com, and others let you take surveys to earn a few miles (and extend your expiration date) on many airlines. Some airlines let you register your credit card to earn a few miles when you eat at certain restaurants, while others let you spend a few miles to subscribe to magazines. Other options exist as well. But if you're just starting out with the points game, it's best to keep things simple and stick with one or two mileage accounts.
* Last-minute fare prices really go across the whole spectrum. If the flight is sold out, they will gladly sell you another ticket, but you are literally paying someone else to change their plans (when they ask for volunteers to accept a few hundred dollars to take the next flight, this is why). If there are a dozen seats left on the plane at the last minute, the fare will often be pretty cheap, whether you pay with miles or dollars.
* Sometimes airline pricing is weird. For example, a flight from A to C (connecting in B) might sometimes be cheaper than a direct flight from A to B or B to C, even though you have to take
both of those flights to get from A to C. There's
a site that will help you search for these weird fares. In my case it's showing me that if I wanted to go from Seattle to Minneapolis on Friday, I could pay $198 for a one-way ticket to Minneapolis, or I could pay $162 for a ticket to Omaha connecting in Minneapolis. Nobody can stop me from "missing my connection" in Minneapolis and walking out of the airport there. Airlines hate this though. So if you do it, buy a one-way ticket because if you buy a round trip they'll cancel your return trip out of spite. Don't check any bags because they'll go to the wrong city. Doing this too many times on one airline could even get you banned from purchasing tickets on that airline in the future. It's a good tool to keep in your back pocket when you really need a lower fare, though.