There are several common challenges and mistakes that candidates often make during the IELTS speaking test:

1. Nervousness: Many candidates get nervous during the speaking test, which can lead to anxiety and affect their performance. It is important to try to relax and take deep breaths to calm your nerves.
2. Lack of fluency: Some candidates may struggle with fluency and may pause frequently or struggle to find the right words. It is important to practice speaking in English as much as possible to improve fluency.
3. Lack of vocabulary: Some candidates may have a limited vocabulary and may struggle to express themselves fully in the speaking test. It is important to expand your vocabulary by reading and listening to a wide range of materials in English.
4. Grammar mistakes: Some candidates may make grammar mistakes while speaking, which can affect their scores. It is important to review and practice basic grammar rules to avoid making mistakes.
5. Lack of coherence: Some candidates may struggle to organize their ideas and may jump from one topic to another without clearly linking their ideas. It is important to practice speaking and outlining your ideas before the test to improve coherence.
6. Lack of eye contact: Some candidates may avoid making eye contact with the examiner, which can give the impression of a lack of confidence. It is important to maintain eye contact and engage with the examiner during the speaking test.

To overcome the challenges and mistakes mentioned above, you can try the following strategies:

1. Practice speaking in English as much as possible: This will help you improve your fluency and vocabulary. You can practice speaking with a tutor, a language exchange partner, or by recording yourself and playing it back to identify areas for improvement.
2. Review and practice basic grammar rules: You can find grammar exercises online or in textbooks to help you improve your grammar skills.
3. Outline your ideas before the test: Take some time to think about the topics you may be asked about in the speaking test and brainstorm some ideas and examples that you can use to illustrate your points.
4. Use body language and facial expressions to engage with the examiner: Maintain eye contact, nod your head, and use facial expressions to show that you are engaged and interested in the conversation.
5. Take deep breaths and try to relax: The speaking test can be nerve-wracking, but it is important to try to stay calm and composed. Take some deep breaths and remind yourself that you have prepared for this test and are capable of doing well.
6. Seek feedback and guidance from a tutor or teacher: A tutor or teacher can provide you with valuable feedback on your speaking skills and help you identify areas for improvement. They can also offer strategies and techniques to help you overcome common challenges and mistakes.