Salvia's prefer a well-drained soil . You can always improve a heavier garden soil with a mixture of compost, mulch and small fractions of lime gravel.
Preferably plant them in the spring and early summer so that they develop a strong root system to go into the winter. Semi-hardy species are best kept in a warm and protected place from the northeast wind. Most salvia's keep full sun , yet there are exceptions. The larger the leaf, the more shadow they can endure.
Never completely prune them in the winter. At the beginning of April you can cut the plants down to 1/3 once they are shooting. Repeat a second decent pruning mid July and you will get exuberant autumn blooms.