Succulents need good draining soil to thrive. If you are planting your succulents in the ground, then make sure the planting area soil drains well. If you have heavy or clay soil, there are 2 solutions. First you can amend the soil with gypsum and Gro-Power to improve the chemical composition of the soil. Here are 2 links to other parts of my blog for tips on using those soil amendments.
Another way to improve the drainage is to create mounds for the succulents. Bring in a few yards of cactus soil, or just add bags of perlite to existing soil in order to have soil that drains well. Ideally you should have 50% perlite and 50% original soil. Mix this new soil with the old soil and create mounds. While you are at it, add some nice rocks from KRC Rock for some terrific material contrast. Here is their web page.
Another way to grow succulents is in containers. Here is a great video from the legendary succulent designer and author, Debra Lee Baldwin, on putting together a great succulent container.