Gutter cleaning is a very important job that is often overlooked by property owners. It's recommended that you clean your gutters at least once a year, generally after Autumn is best. If you have a heavily treed property then twice a year would be best.
Working from a ladder or on the roof is dangerous work and you should always use a professional, don't risk it.
Most home owners are unaware that they may not be covered by their insurance company if the guttering is not maintained and in working condition.