Yeah 사라 is how you'd write your name even though your name actually sounds more like 새라. I have the same problem cuz my last name is 김. It's spelled kim in english but it sounds more like gim. Funny :)

Thanks! Just checking to see if I am on the right track, Only just learnt hanguel yesterday :)

I usually see the first one though.

I would go with the second one. 새 will sound more like the long A in english. Really I think it's up to you (or Sarah) how you would like your name pronounced.