There are many ways to get more facebook likes on your fanpage.
Ways to increase facebook likes FREE >>>>
1- Share it with your friends and tell them to invite their friends.
2- Post it on sites like blogger, digg, stumbleupon.
3- Create interesting topics.
4- Give in a nice thumbnail.
5- Try to more interesting and keep on posting status updates that could be helpful,
6- Connect through other sites like twitter, google+, myspace etc
7- Create a Facebook URL that’s easy to remember.
8- Make a Facebook likes button on your site or tell your friends n family to put it on theirs
9- Turn your customers into fans
10- Link it with your video(if any) from YouTube
Now if you were just doing it for fun then it should be ok to promote through free methods.
However, if you want to promote a business page then I would recommend buying these facebook likes services.
Methods to Buy Facebook Likes>>>>
1-Place ads on Facebook.
2-You could buy it from Buy Targeted Fans
They are by far the best providers in this field and have excellent quality that always gets your fanpage at the top when you search(if you choose bigger packages like me)
3- Run a targeted ad campaign.