Using a dictionary
When looking up a word in a Chinese dictionary there are a number of things to consider. If you know the pronunciation of the word and the word consists of only one syllable the dictionary order is normally alphabetical with the tones providing a secondary order (first, second, third, fourth and neutral tone). If the word consists of one or more syllable the dictionary order can vary. Some dictionaries keep to a strict alphabetical order, others sort on first syllable, followed by the second syllable etc.
Example:
Dictionary 1: gōngrán (公然) before gòngchǎn (共产) - based on the first syllable
Dictionary 2: gòngchǎn before gōngrán - based on the whole word
If you don't know the pronunciation there are two different ways of looking up a character: by radical or by stroke order. The radical method involves identifying the radical and looking it up in a list of radicals. The list provides an index into a second list, which contains all the characters with the same radical. This list gives the name of the character in Pinyin. The actual entries are then ordered alphabetically as described above. The look-up lists are normally ordered by stroke number and type.
With both methods there are some minor differences. Unfortunately, there is some variation in the number of radicals a dictionary assumes (most dictionaries assume around 200).
Here are some common radicals: 亻, 艹, 扌, 氵
Other dictionaries use only the stroke number and type for look-up. This avoids the need to identify the radical in a character, but counting strokes in complex charactes can be quite time-consuming and error prone.
To find a character using its radical you first have to identify the radical.
Count the number of strokes in the radical and look it up in the radical index of the dictionary.
The radical index points to a list of characters containing that radical.
Count the number of strokes not belonging to the radcial and find the character in the index.
This index then gives the name for the character. Use the name to look up the character in the main body of the dictionary.
Example: 明天
明: The radical is 日. The remaining strokes (月) = 4.
Find 日in the radical list (部首目录) under the four strokes entry.
Follow the page link to the list of characters with the radical 日.
Look under the four strokes entry and you will find 明 followed by míng in a Chinese-English dictionary or a page number in a Chinese dictionary.
Finding the radical of 天 is slightly more difficult.
First check if 天 itself is a radical. (It isn't)
If you don't find it try to see if it appears under the radical 一.
Then look for the characters with three additional strokes. Again you will find a reference
to tiān or a page number.
Combine the two characters and look in the dictionary under 'míngtiān'.