Here is an easy way to get 5,000 free Alaska Airlines miles just by printing out your baggage tag at home.
EDIT: The promotion is over. If you would like to sign up for an Alaska Airlines Visa card you can get 25,000 miles upon approval. LINK Full disclosure: if you are approved I also get a bonus of 2,500 miles. You may also be able to find an offer with a $100 credit by starting to purchase a ticket at Alaska’s website and then looking for a credit card sign up link before payment.
If you have status with Alaska or American you can check a bag for free. So even if you normally carry on a bag, this makes it worth your time to check it! This deal is good from today (April 20, 2015) through October 20, 2015. You get 1,000 miles for each flight, up to a total of 5,000 miles during this promo.
You can even request a free tag holder here: http://www.alaskaair.com/content/travel-info/baggage/self-tag-express.aspx
Note that you DO need to have a Mileage Plan number and it must be attached to your reservation. Here are the full details of the offer: