Punctuality has paid off well for me. Seriously, show up to work on time everyday and make everyone look bad in comparison.
Customer service has also been a very valuable experience, dealing with a whole range of people. Learning the art has given me the confidence to interact with anyone, from executive to teenager, co-worker to police officer. Persuading isn't really my forte, but my bullshit detector is well honed.
My advice is get a job in a fast paced but low risk service environment that serves a range of people, the classic example is waiting tables. Master this and then use what you've learned.