You should know what is a complete sentence first. A complete sentence have a subject and a verb. I'm sure you already know what to use when the verb or the subject is in singular or plural. (Ex. The guard is inspecting. The guards are inspecting., My sister sweeps the floor, My sisters sweep the floor...blah, blah) Para matapos na ito, you should read english books and also know the subject-verb agreement...
(Sorry kung yan lang, hindi ko na kaya eh. Pero, sana nakatulong... kahit onti lang)
--Mizu