6 facts you should know about Chinese radical
1. Code of character
There are lots of characters sharing the same part, and meanings of these characters have something to do with that certain part, and this is more than coincidence. We call this part radical.It exists as part of the character before it is applied as the clue to search for the characters in dictionary.Radical (部首) is just the name given later.Characters with this part are essentially related to a certain kind of thing or something related to that certain kind of thing, and that's how characters are formed and the meanings stretch. A new character formed with the radical carries the basic meaning of radical itself, and some specific meaning further, which the radical itself could not reach. For example,氵means water, characters with it as radical （海江湖泊） have something to do with water,but their meanings will be more concrete than water.Relation between meaning of radical and meaning of character with the radical is like that between the general and the specific. An accurate identification of a character's radical could help you distinguish it from its counterparts by revealing what it is mainly about. Sometimes,we may come across confusing characters like 请清情晴蜻氰鲭, but the meanings may reveal themselves if you know the meaning of the radical 讠(talk),氵(water),忄(heart),日(sun),虫(insect),气(gas),鱼(fish). 讠refers to conversation, so 请 (please) is a wording applied in daily communication;清(clear),a description of water 氵; 情(feeling),a mental activity related to heart 忄; 晴 (sunny),a status of weather related to sun; 蜻(dragon fly), an insect; 氰 (cyanogen), a poisonous gas; 鲭(mackerel),a kind of fish. Knowing the meaning of radicals can also help us with the identification of similar radicals like 礻(supernatural being) and 衤(clothes). Therefore, you won't apply 礻by mistake when you try to write the character 袖（sleeve）,which is part of the clothes; neither will you think that 衤will be part of 福 (blessing)，something supernatural beyond your control.
2. A crack on the radical with greater amount of characters first
Focus on the radicals widely applied to tons of characters instead of keeping your eye on those with small amount of example available. So it is wise to pay more attention to several radicals frequently employed. You will find the rule mentioned applies to most of the occasions.Sometimes when it is hard to find the relation between the character and its radical, don't be too hurried to cast a doubt in it.The evolution of characters may leave some original radicals behind. For example,it is unclear why 白 has anything to do with 的，and 宀 with 它.However, if we take a further look into the ancient form of character,the answer is around the corner.旳 is the original of 的，it takes 日(sun) as the radical.旳 means as clear and bright as the sun.And meaning could be extended into "as certain and undeniable as something's existence under the sun", which leads to 旳确 dí què. Here in this word 旳=确. Although its modern form 的 has another pronunciation of de, the wording of 的确 remains. And the transformation of the radical makes the relation between the radical and character confusing. Another case is 它 (牠).It makes sense that 他 (he) has a radical of 亻and 她 (she) takes a 女 as radical. And 牜(animal) acts as the radical of 牠（it）. 牠 is the original of 它, and again the inconsistence of ancient and modern form brings about the mystery. Therefore, if the link between modern character and its radical is weak,try to give an exploration to its ancient form. Drop it if you don't have adequate clue to make the relation make sense. Just focus on what you know applicable. It is a rule self evident and can justify more than half of the stories if it is not for every occasion. Even universal law may have its exception. And what's more, it is a valuable clue for you to link characters together for easier memory.Building connections is the way to make learning less complicated,so if you figure out the path,don't squander it.
3. Memorize the certain radical with its essential meaning and the related characters frequently applied
It is unrealistic to learn radicals separating therm from characters related.It will be a utopian thought to conquer all the radicals and then take a look of the characters and expect that you could open every door with the key you get. Start with the common characters and find the radicals corresponding. Every link you see between the character and its character may mean another strengthening of your belief in mind.
4. Focus on the radical that could be a character itself
There are radicals acting as an independent character itself, and a concentration on them may save your trouble.
5 How to strengthen familiarity with radicals
Practice searching characters via radical; analyse the radical for every new character you come across, trying to see why the meaning has something to do with radical.
6 How to decide the radical of a certain character
If it is a character with a part reflecting the pronunciation (not the 100% pronunciation and probably the vowel of the Pinyin), and another part indicating the meaning, try the part carrying the meaning (清 with 氵). If it is a character with a part embracing another part, try the part outside (围 with 囗；句 with 勹, 函 with 凵).If it is a character with side by side structure, the left part is likely to be taken, but the right part could be the radical if it contains less strokes (姑 with 女; 故 with 攵). If it is a character with top-bottom structure, take the part less incompact (盛 with 皿, 覆 with 覀).If it is a character inseparable,take it as the whole (羊 takes itself as radical). If the radical is not clear to find, try the first stroke to see if you get it right (中 wtih 丨).
Finally, for those who would like to learn more about Chinese radicals, resources available are listed below.
汉字英雄 explanation of radical given by 于丹