How do i know if ETFs are for me?

I’ve been thinking of adding some etf’s to my portfolio. I have no experience with theses and wonder what I need to look out for. I was thinking of purchasing a Vanguard ETF. any advice on what i should look out for when purchasing these would be greatly appreciated. Is there a buying to expense ratio I should look at? I have an account with scottrade if that helps .. thanks in advance.