Steaming or blanching them is a great way to cook them to retain the most nutrients.
To properly blanch beans without overcooking them, place beans in boiling water for 3-5 minutes (until they turn bright green) and then immediately plunge them into ice water.
Simple herbs, olive oil, and lemon juice make a great dressing.
Or, try toasting a ½ c. of cashews in butter or olive oil over low heat for 5 minutes.
Add 2 tbsp. of honey and continue to cook the sauce for another minute, then add to your blanched beans and voila!