Every divorce is different. Depending on the individual factors at hand the divorce process can take anywhere between two months to years. Some factors that can affect the divorce process are:
Naturally, the longer it takes for each party to complete each step in the divorce process, the longer it takes to conclude the process. If the parties are not getting along, this can also prolong the process.
In the end, the best way to assure that a divorce finishes quickly is to try to be as civil with your Ex and as efficient with your time as is reasonably possible.