There are several ways. I'm currently trying to score one myself. You can win one with the promos. Check the promo section of the forum for more information. I will post a link at the end for you.
You also earn points by posting on the forum. The longer your post, the more points you get. This is the way I'm leaning, as I'm not lucky enough to win one. lol. I should warn you, it will take quite a while to earn enough points by posting alone. I suggest you keep a check on the marketplace. There are many people offering points on here that you can complete more than once. You can also create a thread with any skills or services you can offer. You'd be surprised just who might want to hire you. Read all the new threads and see if you can be of assistance to anyone offering credits for your help. I realize none of these are going to get you a domain name overnight...but, every little bit helps.
Finally, you can earn points by referring people to x10. I'm not 100% sure, but I think you earn points just for sending traffic to x10. I know you earn points when someone signs up.
Links:
For the promo section, visit:
http://forums.x10hosting.com/promos/
Especially this thread:
http://forums.x10hosting.com/promos/26293-new-weekly-promotion.html
To begin promoting your referral link, visit:
http://forums.x10hosting.com/referrals.php
I hope this helps. There are also places on the web where you can complete offers and get a domain name, however, it is likely most of them are also US only. Good luck!