Open some additional credit cards, and also consider the business cards (as a sole proprietor for example, selling hawking stuff on ebay/craigslist counts to qualify you).

So you could net some miles w/biz version. Also Starwood Points are transferrable into the delta skymiles program... so if you were to open a SPG credit card you could transfer into skymiles.

You can also buy skymiles.

Or you could fly a lot.