I am prepared for IELTS but worried about my speaking practice. How do I improve it?

1. Get a list of common topics for speaking part 1, part 2 and part 3. Develop ideas on how you want your answers to be. 
2.  Build your vocabulary: There's a whole range of vocabulary that you can build to impress your examiner.
3.  Get the topic: Tape the questions and answer the questions by recording your voice.

When you do that, you think about your grammar, your vocabulary and helps you find your weaknesses.

1. Listen to your answers: Check for 4 things;

1. Fluency
2. Vocabulary
3. grammar and
4. pronunciation

These account for 25% of your marks.

1. Fluency- The first thing you need to check is the length of your answer.  Did you give a very short answer or you could develop it a little more? 

By developing more, you are offering more to the examiner and showing him the ability to speak. 

Another thing to check for fluency is how many times you hesitate. 

How many times you are silent. 

You need to keep speaking naturally with good flow. That will give you a good answer

1.  Vocabulary- Check for the range. 
2. Paraphrasing- are you using the same word again and again or using the same word in different synonyms.
3. Look out for mistakes: When you listen to your answers, listen to how concurrent you are with your speech
4. Check your grammar. Check the range of tenses.

Give a little more emphasis in your sentence by injecting tenses into your answer

Sentence complexion: How complex are your sentences?

Another thing for grammar is mistakes. Practise by correcting your mistakes.

Word Pronunciation: Are you pronouncing the words correctly?

Individual sounds: 

Intonation: If your voice is going up and down or very flat, this is not very good. Use intonation to sound interesting. 

5. The last thing is to get rid of your weakness, improve your strength practice record your voice more and more often.