Some people have a hard time knowing when to put prepositions at the end of clauses or sentences.  There are times where it is ok and then other times when it sounds very uneducated.

It is ok when:

• Infinitive = “Jillian had nothing to work on.”
• When you are using passive voice = “He likes being cooked for.”
• Relative clauses = “They met someone who I used to work with.”
• Questions beginning with who, what, where, etc. = “Who is that for?”

Here are a few more examples to help you out:

• I don’t know who she was with.
• I don’t remember what her final essay was about.
• Who was she listening to?
• We were wondering where that dog came from!
• He has been very stressed lately because of all the pressure he’s been under.
• Their car hadn’t been paid for, so they had to take out a loan.