Your muscle cells, where about 95% of total body creatine is stored, can only hold a limited amount of creatine. Once they're saturated (as happens after 'loading' with creatine), taking more than is required to maintain muscle saturation is a waste: Unable to store the additional creatine, you'll just end up excreting the surplus.
Creatine is carried into your muscle cells by a transporter mechanism. In order to function, this transporter itself requires energy as well as certain minerals (sodium, chloride; possibly magnesium, calcium).
In your body, creatine is converted to phosphocreatine (PC) for storage and transport. As muscle cells fill up with PC, the activity of the transporter declines. This 'down-regulation' may be most pronounced in your fast-twitch (a.k.a. type II, or 'white') muscle cells but affects all types of muscle cells. To avoid creatine transporter down-regulation, Dr. Theo Wallimann suggests consuming creatine for no longer than 3 months at a time, followed by a 1-month 'creatine-free' period.
Note, however, that no studies have been performed to demonstrate the superiority of one method of creatine 'cycling' versus another. Wallimann seems to base his advice on rodent studies, cell studies, and studies of creatine transport.
An alternative to creatine cycling might be to simply consume smaller amounts of creatine each day so as to gradually build your muscle creatine levels up to the point of saturation. Thereafter, consume as little creatine as you need to maintain your gains.
How much is that? About 2 grams of creatine a day. Interestingly, one study found 2 grams to be inadequate to prevent PC levels from falling to pre-supplementation values following the loading phase. However, the gains in lean body mass and exercise performance realized by the subjects were maintained!
Oh, and don't forget: At least in the first 24 hours of use, creatine transport into your muscles can be accelerated by consuming your creatine supplement with carbohydrate (e.g., dextrose, fruit juice).