What's a simple way for remembering the difference between who and whom?

Question

A very simple way,

Plus is it This is she or this is her?

Answer 1

Who is the actor/subject and whom is the receiver/acted upon.

Who ran the race?

You told whom?

It depends on the relationship to the verb/action word.

Answer 2

Somebody taught me that an easy to see which works is to see whether he/she or him/her would work in the situation. If it's he/she use who; if it's him/her use whom. i.e. "Who wrote the letter?" = "He wrote the letter."; "For whom should I vote for?" = "You should vote for him." If you get stuck switch the sentences around like I did for the second example. I hope that's a help.

As for this is she/her, I presume you mean as though you're on the phone. I've looked around (the internet) because I never thought about it and apparently they're both right. (My Source is to a website with a huge argument about whether to use 'this is she' or 'this is her' and I don't think they've got an answer.)