In the northern states, where the sun is not as strong, full sun may work but in the southern half, some afternoon shade is required. Hydrangeas are understory plants and will do best with morning sun and afternoon shade. Dappled sun will work too. Keep an eye on the leaves during the summer. If you notice sunscald only on the leaves that have direct contact with the sun, it may be necessary to move the shrub to a shadier spot. If you do not notice problems then leave it there.

New stems are not that strong at first (like for example in H. arborescens Annabelle) so feel free to assist them in their first few years. Some people put chicken wire around the base of the plant and tweak them during winter when the leaves have dried out and the plant parts are more visible). Heavy blooms and weak stems are the usual causes for stems to droop. As the stems get older, they will be stronger but, for aesthethic reason, it is best to provide some support, especially for times when the blooms get large and are wet from rain or sprinkler water.