Succulents need two things to be happy; full sun, and excellent drainage.
The full sun part is a fixed factor. Don't place your garden in shade, or even partial shade. Aim for at least six hours of sun.
The drainage part of the equation is something you do have control over.
Raised beds, rock walls or other system that raise plants up off the ground make for happy succulents, and combined with fast draining soil (even if you have to bring it in) this is all they need.
Stacked stone walls, without any kind of mortar, give you lots of places to set the plants in where they'll get warmth, a tiny bit of moisture in behind the rocks, and, good drainage.
Raising the soil up off the ground, especially in areas that have clay soil, gives the succulents their best chance of success.
Wet soil causes the delicate, fleshy roots to rot, so drainage is essential.
Mounding up the center of the raised bed with soil also helps.
You can place larger rocks or even driftwood to act as retaining walls, putting the succulents higher up. All of these techniques give succulent plants the best outcome.
This mounding technique also puts the plants up higher so you can view them.
They naturally grow this way in their original habitats, aiming to get more light without the competition that makes them stretch.
Mulching with pebbles, lava rock or other mineral mulches not only makes the garden look nice, it also prevents weeds from making a foothold, and keeps some moisture under the mulch.
See more about weed free xeriscaping here.
This can mean the difference between a garden that struggles, and one that is basically maintenance free, including irrigation.