Use 'Dear Sir/Madam' and put the name on top.

>What if I omit Ms. and just write
>
>Dear Lauren LastName,
>
>...
>
>Or
>
>Dear Ms. Lauren ... is better ?
>
>
>>Female
>>http://www.zelo.com/firstnames/findresults.asp?name=LAUREN
>>>Hi everybody,
>>>
>>>I'm writing a letter to Lauren and need to know how to proper address this person. I started Dear Sir, but then had second thought.
>>>
>>>What do you think?
>>>
>>>Thanks in advance.