Study the subject and the predicate. The subject is a noun or pronoun. This can be a name, a person or an object, for example, "Jim." The predicate is a basic set of information containing at least one verb, for example, "has." A predicate may also contain a noun like "cat" and an adjective. So the sentence would contain the subject plus the predicate, this makes "Jim has a cat."
Learn about the difference between the subject and the object. The subject is someone or something that does the verb. The object is the person or thing that the verb is done to. A verb is an action. Here's an example: "Jim fed his cat." In this sentence "Jim" is the subject, "fed" is the verb (past tense of feed) and the "cat" is the object. Note the sentence structure; it is subject then verb and then object. This is the most common sentence structure in English.
Study clauses. Each clause contains a subject and a predicate. Sometimes a sentence can contain more than one clause. This can be a compound of two clauses joined with "and" or "but" such as, "Jim likes cats, but his sister does not." There are also complex clauses. These contain a regular clause and one that depends on that clause joined using "because," "although," "where," "which," "since" or "that." For example, "Sharon does not like cats because she has an allergy."
Move on to study possession. Possession is where one object or subject belongs to another, for example, "Jim's cat." You will see the sentence structure is "owner" plus "thing owned." Jim is the owner and the cat is owned. In English the apostrophe (') plus an "s" is used to show possession. If the word ends in an "s" such as, "Augustus," then you can add just the apostrophe to make "Augustus'" since adding a third "s" makes pronouncing the word difficult. If, however, a word has only the one "s" at the end, such as "bus," then adding an additional apostrophe "s" is not a problem: "bus's."
Ask yourself a question. How does it sound? Steps 1 to 4 teach you the basics of declaration statements such as, "Jim likes cats." The syntax rules for asking questions are different (see Reference 2). With a question the word order is slightly different. The first word is now the modal verb, and the subject is second, followed by the actionable verb and finally the object. A modal verb asks a true or false, yes or no, question. For example, "Does Sharon like cats?" In this example the modal verb is "does." Other modal verbs include "will," "shall," and "can." There are also question verbs that ask for a more detailed answer. These include "what," "why," "where," "how" and "when."
Learn the difference between active and passive. The examples used in steps 1 to 5 are active. The subject is doing the verb. A passive sentence will reverse the subject-object syntax so the verb is done to the subject. Passive sentences usually contain the word "by" before the subject. The passive voice is formed with an auxiliary verb. An auxiliary verb gives more information on the main verb. This is usually a form of the "be" verb. For example, an active sentence is "Jim owns a cat." A passive sentence would be "The cat is owned by Jim." Here "is" is the auxiliary verb and "owned" is the main verb. Practice by converting active sentences into passive.
Buy a course book on syntax. Steps 1 to 6 have taught you the basics of studying English syntax. However, it is more complicated. These basics will allow you to communicate, but to learn more you will need to study more advanced books. A quick internet search will show you a number of learning resources, too.
Copy down new sentence constructions. Whether you are reading a newspaper or a letter, write down or copy and paste any new sentences you see. Break the sentence down into its core parts. If you get stuck, consult your text books. Don't be afraid to ask friends or a teacher for help if you need it.