I know that most of us knew this method already, but I wanted to give it an emphasis since we were going to start paragraph writing soon.
Words are the primary tool in writing a sentence, and sentences are the primary tool in writing a paragraph.What I am trying to say is that, we need to have a wide range of vocabulary in order to express the idea that we are trying to convey. And one good technique that my teacher told me, back in my high school days, is that, we need to learn at least a word or two each day. Another one is by listing down and searching word meanings that are unfamiliar to us whenever we encounter them through movies or normal conversations.These techniques are the best exercise, aside from reading, to fill up our word banks.
I hope you would try them if you haven't yet. Remember that there is no lost in trying. Good luck and God bless us all.