1) Study the parts of speech:
2) Study how the tenses of verbs: Simple, Perfect, and Progressive
3) Subject-verb agreement: The verb must agrees to its subject in the sentence.
4) Sentence Structure and Types/Functions of Sentence:
Basic Sentence patterns:
S - TV - DO
S - TV - IO - DO
S - IV
S - LV - C
(S= sentence; TV= transitive verb; IV = intransitive verb;
DO= direct object; C = complement)
5) Transforming Active to Passive and vice-versa.
6) Expand your vocabulary. Whenever you encounter a word whose meaning you're not familiar with, check its definition, part of speech, pronunciation (you also have to be familiar with IPA symbols), and example of its usage.
7) If you have regular access to internet, you may check websites with free simple lessons for non-English speakers (ESL websites), or local library with textbooks on Language.
8) Practice writing your text messages without abbreviating a single word.
9) Finally, read, read, read. Read comics, newspapers, books (there many classic literature in public domain, meaning free to download without violating copyrights), textbooks, school/office memorandum, brochures and manuals. Choose a sentence, then identify the part of speech to which each word belongs. Write an essay about current issues, and have it checked by someone you know could help you edit your work. Keep a file of your materials. If you have Tagalog materials, try translating some simple sentences into English. Then arrange them according to sentence structures/pattern above. Begin with simple sentences.
Remember grammar is not about talking in twang; it'snot about writing long sentences nor using difficult to understand words to impress your readers. Grammar is simple - using the parts of speech properly and correctly. Remember to write and talk in active voice when passive is not required.
Also, "yes" is "yes", and not ya, yeah, yo.
I don't know is not I dunno.
Happy learning :-)