Find a straightforward English sentence from a source whose grammatical accuracy you trust. If you're not a native speaker of English, ask someone who is to verify for you that the sentence contains no errors. Here's an example: "It was a bright cold day in April, and the clocks were striking thirteen." (That's the first sentence of George Orwell's "1984.")
Copy the sentence you found by hand, leaving plenty of space for notes. Also copy the example sentence above so that you can use it as a reference.
Locate the words in these sentences that represent a person, place, thing or idea, and mark these with the letter "N." These are nouns, which refer to who or what is doing something in a sentence, or else something is happening to them. In the above example, "day," "clocks," and "April" are easily recognizable nouns.
Scrutinize the sentences to seek out the less obvious nouns. In the example, "thirteen" is a noun, because the author is using it as a concept. The first word of the sentence, "it," is also a form of noun; it is a pronoun, a kind of word that takes the place of a noun, like the word "he" in place of "the boy." Mark all these sneakier nouns, using "P-N" for the pronouns.
Underline all words that refer to an action, which are the verbs. Mark these with a "V." Verbs are the most structurally powerful parts of speech; you can't have a sentence without them. In the example sentence, the only obvious action is "were striking." Both these words form the verb, or in this case, a "verb phrase." A more subtle verb is hiding at the beginning of the sentence: "was," a form of the verb "to be." Think of "being" as an action of existence.
Examine your nouns and look for neighboring words that describe them. Mark these "Adj" for adjective. In the example, "bright" and "cold" are adjectives describing "day." Remember, though, that a sentence is not required to contain adjectives or any parts of speech other than a noun and verb.
Find and mark the words that describe your verbs, labeling them "Adv" for adverb. Adverbs are easy to recognize, as they usually end in "-ly." Orwell used no adverbs in the example sentence, but if he had used the adverb "noisily" to describe "were striking," it would look like this: ". . . and the clocks were noisily striking thirteen." Adverbs can also be used to modify adjectives. If Orwell had written, "It was a bitterly cold day," "bitterly" would be an adverb intensifying the adjective "cold."
Focus now on words that convey a relationship between other words in a sentence. Mark these "P" for preposition. In the example sentence, the only preposition is "in," which expresses the relationship between the "day" in question and the month "April." Prepositions are usually short words, such as "for," "with," "by" and "to," but they carry a lot of structural weight.
Mark conjunctions, words that connect words or clauses to convey order or causality, with the letter "C." In the example sentence, "and" is the only conjunction. Other conjunctions include "but," "or" and "because."
Comb through your sentences to find any words that are still unmarked. You are likely to find articles, "the" and "a," which are small words that give nouns a sense of number and specificity. Mark these "A."