Besides the perks, most airline credit cards come with lucrative sign-up bonuses. There's really no limit to the amount of bonuses you can get, but you do need to understand the effect that multiple cards can have on your credit. As long as you pay your bills off on time, you should be able to apply for the bonuses you want.
Just make sure the annual fees of your cards do not negate the value of the perks you receive as a cardholder. You can also cancel a card to avoid the annual fee or downgrade to a card with no annual fee from the same bank to maintain your credit line.
Once you get the miles, one of your most important allies in getting the most from them is airline alliances. Most airlines are members of the three global alliances: Oneworld (American, British Airways, Cathay Pacific, Qantas and others), Skyteam (Delta, Air France/KLM, Korean Air and others) and the Star Alliance (United, Lufthansa, Singapore and others).
That means you can earn miles that go into your primary frequent-flier account when you fly on that airline's partners. For instance, when flying Air France, you can earn Delta miles because the two are part of the same alliance.
The same is true of redeeming miles. You should be able to use your frequent-flier miles for award tickets on an alliance carrier. Thus, you don't need to redeem United miles just for United flights, but you can redeem them on Lufthansa or Singapore, among others.
Get the awards
Airlines don't always make it easy to use your miles. Some airlines don't even let you search for award seats on their partner airlines. Here's the most important thing: Don't give up.
Other people will give up, but you can use this to your advantage because it means there will actually be more unclaimed award seats for the picking.
More advanced frequent fliers use tools such as ExpertFlyer.com, which isn't free, to search for open award seats on specific flights and also set alerts so that when award seats become available, they receive email notifications. You don't constantly have to check for availability, and you will have the edge against other fliers looking for those same awards. It takes some practice to understand the ins and outs of it, but if you fly a lot, it can save you time and money to make it worth it.
Not surprisingly, airlines have gotten crafty at charging extra fees, including fees on award tickets. Many of these fees are waived for elite members, which is one reason that giving loyalty to one airline can ultimately pay off in more ways than just free upgrades.
Common fees include late or close-in booking fees; most airlines will charge around $75 for booking a ticket within three weeks of departure. The solution: Try to redeem with airlines (Delta and British Airways, among them) that don't charge those.
Many airlines require you to book complicated or partner awards by phone but charge a $25 fee for doing so. The solution: Always request that the fee be waived because you could not book the ticket online. In many cases the airline will comply. It never hurts to ask.
Some airlines (US Airways and Delta, for instance) charge $150 to change an award ticket, but others (American and United) will let you make date changes free if you keep the departure and destination the same. Solution: If you think your plans might change, go with the fee-free.
The true measure of your miles' value is whether they get you where you want to go. Do not let them expire, don't let them go unused and do not assume they are worthless. My miles have allowed me to travel the world for pennies on the dollar. In the end, if you are happy with your redemption and your miles saved you money, you've received good value for them. And that's all that really matters.