Start off by smoothing out any bumps or nodes. To do this don a pair of work gloves of the latex/rubber variety. Use sand paper and/or steel wool to smooth everything out nice and even.
Okay, you did that, now you need to brush off the entire surface. (Yeah, you can take a hose to it and rinse, but then you have to quickly dry the table so that new rust won't start up).
Next use a metal paint (that is, a paint specifically made for painting metal). Paint evenly (use a brush, spray paint often leads to random bubble-drops and screws up the appearance). Let it dry. Feeling ambitious and generous? Go for a second coat. This will help protect your table from an occasional bump or hit.
For extra pizzazz you can add an enamel finish or a shiny clear lacquer.
Do all work outside with good ventilation. Your respiratory system will thank you.