Rhododendron's and Azalea's require a chalk-free, humus-rich soil with sufficient moisture. When your soil is non-acid you will need to amend it. These plants love peat moss and leaf-mould. Never fertilize these shrubs with regular fertilizer use a acid fertilizer. Also add a mulch of shredded pine bark and peat moss mixed, when this compost rots it will provide the plants with all the elements they need. This will help retain moisture and keep the roots cool, which are very thin and near the surface.
As far as pruning do not prune in the fall, you will be removing next years flower buds and forcing the shrub to produce new growth which will be damage in the winter months because they are so tender. Prune now, or right after blooming when the new growth starts if needed, most of the time I remove the new growth selectively where needed. This keeps my shrubs in the shape I want.
Another great tip remove the seed pods left from the flowers. When allowed to stay on the shrubs they take strenght from the shrub. Plus you have a neater shrub with those dryed flower spikes removed.
