Know your succulent:

Different succulents have different cultivation needs. The reason for this is that environmental conditions are different in different succulent habitats. To successfully grow succulents it's important to know something about the environment they evolved in-particularly regarding rainfall seasonality. The arid regions of the world differ greatly in terms of water availability and this will influence how you should grow a particular succulent.

For example succulents may grow in environments where:

it mostly rains in the winter and is mostly dry the rest of the year

it mostly rains during the summer

it mostly rains during the spring and fall  

it rains very little and plants acquire most of their moisture from fog

it may rain very little all year long

Depending on rainfall availability different succulents evolved different growing seasons. For instance, plants that evolved in areas of the world where it rains during the winter  will tend to grow during the winter and go dormant during the summer. In cultivation watering a plant too much outside of it's growing season can cause problems and, depending on the succulent, can lead to fatal rot (plants are more susceptible to the bacteria and fungi that cause rot when they are dormant).

Succulents tend to be described by succulent growers/enthusiasts as "winter growers" or "summer growers"; Winter growers are to be watered mostly during winter and  summer growers mostly during the summer. While this classification is an oversimplification (see above example of different rainfall patterns) it has proven useful in guiding when a particular plant should be watered.

Adaptability is also a factor in dictating how to care for plants: Some succulents are extremely adaptable and  will happily grow all year if watered outside their growing season.  Others succulents (lithops are a good example) will quickly succumb to rot if watered outside of their growing season. Most succulents are inbetween these two extremes. Knowing when to water and when not to water often requires intuition and is the key to success in growing succulents.

The Internet is a good source for information about succulents . The cactus mall is a good place to start (http://www.cactus-mall.com/). The Dessert Tropicals website: (http://www.desert-tropicals.com/) has some information about the habitat of many succulents. 

Some broad oversimplified guidelines based on my experience and base of knowledge:

Generally most cacti in cultivation do best as summer growers and should be kept dry in the winter. In my experience watering most cacti when it's cold can lead to rot. However some cacti adapt to being watered in the winter: here in California I have cacti (mostly opuntia, echinopsis and trichocerus) planted in the ground that are rained on all winter and they seem to do fine.

African succulents either come from winter rainfall regions, summer rainfall regions or regions where most of the rain falls in spring and fall. With the exception of Lithops and other mesembs, most african succulents will benfit from more water than cacti. If you acquire a south African succulent find out what season it gets rained on most in habitat and water accordingly.