Fill a bucket with perhaps two liters of cola (it can be any brand). Soak the golf clubs for up to five minutes (don't forget about them). When you take the clubs out, rub them dry with a soft handcloth. As long as the clubs aren't irreparably rusted, this may do the trick.
Using a dish soap such as Dawn, make a bubble bath for your clubs. Submerge the clubs for a few minutes, take them out and wipe them clean with a toothbrush. The toothbrush is unique because it gets deep into the grooves of the club.
Use a rust remover, such as CLR (stands for Calcium Lime Rust) should do the trick. Follow the bottle's directions, which should just include covering the golf club in rust remover and brushing them clean with a toothbrush or cloth.
Try taking the clubs to a local golf store, where they may more accurately assess the damage of the clubs.