If you were able to ask your spirit guide (a.k.a. your guardian angel) one question, what would it be?
It is hard to narrow it down to just one question.
Ask more than one question then.
Ask for them to guide you towards the answer in a way that you will easily understand. Meditation is one way you can receive the answer to your questions. Sometimes you will notice the answer when you overhear a conversation, see a physical sign or by listening to a song on radio (or one that seems to play in your head). These are all ways you can receive an answer to your question.
I believe they are there to help us in any way they can. We just have to ask … anything.
And … when you hear the answer, thank them.