The reactions of other characters:
How do other people behave around your character versus how they behave around anyone else? Better yet, what are their reactions to your character when they are not around?
There's already been a lot of posts about this, but the way your character carries themselves can help you reveal their mood. However, the meaning of the body language may depend on the situation and circumstances. For example, crossing your arms can signal both defensiveness or confidence.
What does your character like to do for fun? Is it considered an introverted or extroverted activity? Why do they get joy out of it? Did they take up the hobby because they really wanted to do it, or for someone else's benefit? (for example, Shinji from Neon Genesis Evangelion mentions the only reason he never really stopped playing the cello was because no one told him to stop, even though he admits that he doesn't like playing the cello very much.)
How does your character speak? There are a lot of things that can influence the way a character speaks, including the person they are speaking to, their culture, and their background. For example, how does your character speak to someone with authority over them versus a group of their friends?