Plunge beans in pot of boiling salted water to cover. Turn down heat and simmer for 5 minutes. (Test the beans to see that they are "al dente" but not chewy)
Drain and refresh beans under cold water.
Drain and place in a ceramic or glass shallow dish.
Sprinkle with garlic, dill sprigs, dill seeds & mustard seeds.
Put vinegar, water, salt & sugar in a pot & bring to a boil until salt & sugar dissolve.
Pour hot mixture over beans.
Allow beans to cool in mixture. Then chill in fridge, covered for at least 24 hours - up to 2 weeks (if they last that long!)