There are basically some basic rules for taking of lilac bush those are choosing the planting side,sunlight, good drainage, provide good soil and pruning.
Pretty much all you need to do is plant them make sure the soil is covering the root base and then water and that should be all you need to do for healthy shrubs.
Prefer an alkaline soil with rich in nutrients.A position with enough sunlight and shade is good for this plant because the food remain protected from heat.