You can earn a premium account easily and quite fast. All you have to do is to,

1. Create a free PayPal account at http://www.paypal.com (Hit cancel when it asks for credit card info).
2. Register to a fast money producing site as the following ones,

http://www.bux.to
http://www.adbux.org
http://www.paid.vg
http://www.awsurveys.com
http://www.getref.com
http://www.taketheinternetback.com

3. You can earn money by clicking on the ads mentioned in the above sites. When you have enough money in your PayPal account (which shouldn't take long), you can buy yourself a Rapidshare Premium Account. Payout limit is only $10, you'll get to it in no time and it is worth of a 2 month premium membership.

You can also look at the following sites for more info

http://freerapidsharepremiumacc.oyla15.de/cgi-bin/hpm_homepage.cgi
http://www.paypal.fmsfreebies.com
http://www.rapidshareaccounts.tk
http://earnmoneyeasily.blog.com
http://ptctalk.blogspot.com

Good luck!