When to capitalize them:
You only give them a capital if the title replaces their actual name. For example:
When is Mom coming home?
When is Rita coming home?
In this case the word "Mom" replaces the mother's name, Rita.
When not to capitalize:
When you are placing an article or pronoun before the title. A good way to see if the title needs a capital is to insert their name and see if it makes sense. For example:
When is your mother coming home?
When is your Rita coming home?
Is the teacher here yet?
Is the Mrs. B here yet?
The second parts of each example don't make sense, so I know that the titles shouldn't be capitalized.
Hopefully that makes sense. If you have any questions or think I might have missed something, please feel free to comment.