Example 1
My mother-in-law doesn't know that the reindeer sweater she loaned me is for my office's ugly Christmas sweater party.
We won't tell. We will, however, tell you that since mother, in, and law work as a unit to form a compound noun here, you should use hyphens to connect them.
Example 2
Barry started the season on the B-team, but by the playoffs he was the Chargers' starting point guard.
Way to go, Barry. In this example, we use a hyphen to join the letter B to the word team because we have championship-level grammar skills.