How much sun succulents need
Since you're growing your succulent indoors, pay attention to the color of the succulents you're purchasing and tend toward the green ones. Brighter succulents with colors like orange and purple might look pretty, but they'll likely require more sunlight than you can provide, so stick to the darker, heartier ones.
Green or not, supply them with as much light as possible. Outside they want something like six hours a day, but inside don't even think about it in terms of hours. Just get them in the sun and keep them there. Place them near the window that has the most light per day in the brightest area you can manage, as close to the window as possible.
You'll be able to tell if your plant isn't getting enough sunlight if its leaves start to stretch. Your succulent child is bending and expanding in a feeble attempt to get as much light as it can, so the least you can do is move it closer to the window or to a brighter area. If that's not possible, you can look into purchasing a grow light, which mimics sunlight and could save your little plant's life.