If your credit is good, and you can handle the credit inquiries, by far the easiest and fastest way to accumulate airline miles is by getting the huge sign up bonus miles that many cards are currently offering. Credit inquiries can lower your credit score by small amounts at a time, so you don't want to be careless about it...but if you do it wisely, you can pile up a ton of miles. I've built up 400,000 miles in the past 4 months, including attaining status without flying, all by credit card sign up. Here are two popular blogs that have info:

www.frugaltravelguy.com
www.thepointsguy.com/