Sometimes hesitation is difficult to avoid, but there is a right way and a wrong way to hesitate when you're struggling to maintain fluency.
When the examiner asks a question, do not start answering immediately unless you are confident that you are ready with an answer.
Don't do this:
I believe that [pause for 3 seconds] it is very difficult to stamp out corruption completely.
Instead, do this:
[pause for 3 seconds] I believe that it is very difficult to stamp out corruption completely.
By giving yourself time before answering, you are more likely to produce a complete sentence wihout any more hesitation.
If you really need to pause mid-sentence, then at least give your listener meaningful sentence chunks.
The chunk I believe that - on its own - does not carry very much meaning, and the listener has to hold it in his/her head as he/she waits for the next chunk.
Longer, more meaningful chunks make it easier for the listener to complete - mentally - a sentence that contains hesitation.
Chunks that are difficult to join in order to complete the sentence mentally
Chunks that are easy to join mentally - even if there are longer silences in between
Instead of silence, native speakers often use fillers as a way to 'buy time' while they are thinking about how to answer a question or how to continue an idea.
These are useful some of the time, and you will certainly hear native speakers using them. However, try to keep them to a minimum. At least try to combine them with other, more sophisticated fillers.
Before we look at some fillers that native speakers might use, remember you must use them appropriately. Your choice of filler will sometimes depend on the type of question and/or the content of your answer.
The following would not be appropriate:
In this exchange, there is no excuse for hesitation - you should know by now whether or not you have any brothers or sisters. Also, there is nothing interesting about this question.
Fillers that you might hear from a native speaker..
..in reponse to a question:
..pausing before continuing an idea or line of thought:
Actually when developing your ideas, almost any signal - together with a pause - will behave as a filler and will buy you time while you think about what to say next.
Fillers need to sound natural, so make sure you have memorised them, and make sure you are using them appropriately. The whole point of using fillers is that you don't have to think about them - you should be thinking about what you're going to say next while you are using the filler!
Remember that too much hesitation in IELTS speaking can bring down your score for Fluency and Coherence (FC).