When we have rain, like the last couple of weeks, I wouldn't worry about watering at all. On the other hand...
Later in the summer, we may go through a dry spell in which case you will want to water regularly.
Mostly though, it depends on the plants.

Plants that prefer dry soil like Achillea(yarrow), Liatris, rudbeckia(Coneflower),etc. would not need much watering.

Plants that need moist soil like sweet-flag, creeping jenny, etc. would need watering most every-day in cases of no rain.

Watch your soil. And try and plant species that prefer the same moisture level together.

About lilacs....You haven't seen many Lilacs planted here in Alabama because they typically do not grow well here. There are a couple that are supposed to grow here. But my experience, even with these varieties has been that you get flowers, but not those great big ones like up north. Our climate is just too darn hot!!!

Plants and turf should only be watered when they need it. I know that sounds flippant, but that is the best way to put it. Water deeply but infrequently is the general rule, and that goes for grass, too. If you have clayey soil, then you will learn that plants can go for quite some time without added water.

I do not have an irrigation system (don't believe in them). Last summer, I watered my established lawn twice!! It slowed down growing, but never showed any sign of distress. We put in two new perennial beds last year, and I kept them watered as needed, but never watered the established trees and shrubs. Never.

What kind of soil do you have? I had a consulting job in Decatur last year, and was pleasantly surprised by the rich, dark, loamy soil I found in my client's yard. It was wonderful stuff! Are you that fortunate?