Around 90% of Chinese characters are composed of a meaning component ("radical") and a sound component ("phonetic").
Usually, you write the former on the left hand side, and the latter on the right hand side. This is only a general rule because there are also radicals that can be found on the top of a character, on the bottom, as well as on the right.
In the 說文解字/说文解字, ( Shuō wén jiě zì ) a dictionary compiled in the 2nd century CE by Xǔ Shèn (許慎/许慎) the over 9000 characters contained in the work were categorized under 540 section headers or radicals. This number was reduced to 214 in later works.
Here are all of the 214 traditional radicals. They are arranged by the number of strokes needed to write them. To see how they are written in isolation, just click on the radicals. [only radicals 1-120 are implemented at present]