Record yourself
Often when you are speaking, you do not realize how many mistakes you make or what they are. You will be surprised that you can actually pick up many mistakes if you replay your talk, and by copying it down, it will probably bring out even more errors. Once you have noticed your most common errors, get yourself a grammar practice book and practice your weaknesses.

Take part and reconstruct sentences
Open up any book and choose a sentence. Break up the sentence into smaller sentences and then without referring back to the original sentence see if you can put it back together again. In the IELTS, you will need to be able to produce both short and complex sentence forms. You will not get a high score if you only use short simple sentences for the sake of accuracy.

Practice linking words and expressions
The easiest way to make a sentence sound more complex is by using a linking word. Get yourself a grammar book and practice using conjunctions and linking words.

Read, read, read
The more you read the more good grammar you will come across. The more accurate and complex grammar you are exposed to, the more likely it is that some of it will rub off on you.