Too much waste in your gutters can clog them up and defeat the purpose of having rain gutters in the first place, with all the waste and dirt damming up the rain water. The accumulated water plus the weight of the waste left behind can damage your gutters through time, so it is important that they are kept clean all the time.
It is recommended that you clean your rain gutters regularly, before the rainy season starts. Be sure to not let the debris and detritus gather as this will be much more difficult to remove when you leave them alone for a long time. If you clean your gutters regularly, it will be a short and easy task as there is not much dirt to clean off, compared to when you just leave trash to gather there. It is important to remember though, that more cleaning is needed when there is a tree over your gutter or when you live in an area where it frequently rains.
Take the right safety precautions when working on your gutters - use the proper safety equipment such as protective gloves and use a very sturdy ladder that is set firmly on the ground below. If you must work from the roof (which can be easier in come situations), do so only when it has a lot pitch. Never work on the roof when the surface is wet or strong winds are about. A weak gust might not blow you off, but it can set you off balance and cause you to fall.