This one is easy: there should be a wedding or talk of a wedding or a bride etc in the trailer.

Last week we saw trailers for:

• Jupiter Ascending
• Our Family Wedding
• Just Married
  
• Melancholia
  
• The Wedding Ringer
  
• Prelude To A Kiss
  
• Stepfather II: Make Room for Daddy
  
• Maybe I Do
  
• Best Friend from Heaven
  
• Bubble Boy
  
• Seven Chances
  
• He Knows You’re Alone