Dont spend too long on it, or you will stress yourself out.
Stay calm, they are not trying to catch you out. Dont inturupt them, only answer questions they have asked about, dont waffle, get some questions ready.
If they ask about your interests, keep them brief, they dont want to know you spend hours on car forums and what you talk about

No interview is the same, if they are uptight then stay serious, if they are more laid back then being similar is fine, if they are jokey then laugh with them etc etc