The art of Bonsai is an ancient and beautiful connection. I do not profess more knowledge than what I have researched regarding the Juniper Bonsai. This particular variety is the procumbens 'Nana'. There is an abundance of conflicting information regarding care. The following information is a culmination of recommendations from many sources and includes what I believe to be the best method for caring for the Juniper Bonsai in Virginia. As I gain more knowledge, I will update this information. As with any plant, I encourage you to do your own research and learn as much as possible about your new plant.
If you purchase your Juniper Bonsai during the winter, for the remainder of the winter, keep your bonsai indoors in a bright location (ideally near a south-facing window). Water just before the potting mix becomes fully dry taking care not to keep too wet.
In the spring, place your bonsai outside where it will receive several hours of direct morning sunlight and shade during the most intense heat of summer afternoons. Protect from frost in the early spring. While outside spring through fall, water before the mix becomes dry throughout the pot. Never let your bonsai sit in standing water. Trim to train and shape but never cut back all new growth.
Next winter, place your bonsai in an unheated garage or other dark and cold protected environment for dormancy (approx. 3 months). Water only when the potting mix has become fully dry (about once every 3-4 weeks). Bring it outside once again in the spring. Use a diluted liquid fertilizer once or twice a month spring through fall.