If you've ever watched a Bruce Lee movie, you're probably obsessed with them anyway. So, let me give you some tips.
1. Check the laws in your area. Nunchuks are illegal in some states. In others, they're legal for training purposes but must be carried openly when you're transporting them from your house to your car. Carrying them in a bag constitutes carrying a concealed weapon. (I ignored my own advice once when moving from one state to another and lost my precious rosewood set to the Po-Po. Strangely, I was allowed to keep the small but very real dagger attached to my keychain, a gift from an ex that I kept because it was cute.)
2. When you're learning to use them, always buy a padded training pair. You will hit yourself many, many times. A padded pair will hurt like hell. An unpadded pair could land you in the hospital.
3. There is a difference between classic nunchuks and freestyle just as there is a difference between the real martial arts and freestyle arts. Learn the differences and decide accordingly. Please note that many traditional martial artists will not be impressed and do, in fact, feel that "freestyle" demeans the arts. (Generally, if someone tells you they obtained a black belt prior to their mid to late teens, they did not study classical martial arts.) The traditional arts aren't nearly as flashy/acrobatic as what you see in many U.S. competitions and demonstrations. They are, however, deadlier.
4. Pick your instructor carefully and make sure that person is certified to instruct in the style you want to learn. For most purposes, learning by video isn't the greatest idea. You should have someone who can be there to adjust your grip, stance, etc. You may also want someone there the first time you nearly knock yourself unconscious.
5. Many have mastered the art before you. In many cases, they are way better than you will ever be. So, don't think this makes you the ultimate badass.
6. Handle your weapon with humility or it will handle you.