Many people end up having many job changes frequently inadvertently. This fact lands them in a soup whenever they go for interviews.
Generally even in a strong economic condition, keep your job with one employer for at least 2 years. Less than 2 years of working with any employer is not a good sign in the eyes of most employers. They feel that the candidate is not serious about his own career. They feel that the candidate is very opportunistic. So if he employs him, he may not stay with him for long.
First and foremost, you should know that it really is a bad thing to keep changing jobs for no plausible reasons. So never change jobs on whims. If you still end up having changed jobs frequently then here are some tips to overcome this negative aspect.
Find out some plausible explanation for your job changes. Some of the good reasons could be, inappropriate location of the office of the past employer for you and commuting was a problem for you. You upgraded your skills and the past employer had no vacancies where you could utilize your new learned skills. You needed to shift to a new city because your spouse found a new job in that new city and you needed to quit your present job to accompany your spouse.
Try to think some convincing answer for your need to change jobs frequently. The answer must contain some very convincing answer.