"Because" is a subordinating conjunction and, as such should be used to join two clauses. But did you notice that my sentence began with because and is correct.
Or try this one: "Because it was hot outside, we decided to go to the pool." Also correct.
However, as one of my tutors (at JCU) pointed out, the rules of grammar are there to help the reader understand what you mean. If the meaning becomes clear by breaking a rule then out comes the sledgehammer and WHACK!
Because I know what you're talking about, yes.
If you are asking about proper grammar:
Many people have been taught that it's wrong to start a sentence with a conjunction, but nearly all major style guides say doing so is fine - See more at: http://www.quickanddirtytips.com/education/grammar/can-i-start-a-sentence-with-a-conjunction#sthash.uKSopGNe.dpuf
If you are asking about punctuation:
No sentence starts with "because ," because "because" is a conjunction.
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