Talk to the custodian with the same respect you’d give the principal. People notice who you’re polite to.

How you treat people who hold no power over you is the most honest information about you available. Politeness pointed upward is easy and proves nothing, since it might only be ambition wearing manners. Everyone notices the difference, including the people you were trying to impress. Character shows up in the places where there is nothing to gain.

Learn the names of the people in your building who usually get walked past, and use them. Say good morning first. Do it consistently rather than visibly, because the moment it becomes a performance it stops counting for the only reason it mattered.