The first year of your lavender plant is when it's most fragile. After that, very little care is needed to maintain a beautiful shrub. Here are a a few tips for the first year:
As the lavender plant becomes established in its first year, it will start sending off small shoots of buds and begin flowering. Resist the urge to enjoy these flowers. It will be best in the long run to trim these buds back. This will encourage the plant to spend its energy into good root production. You will be rewarded for your restraint since your lavender plant will double in size the second and third year planted.