Although this is a speaking test, a good way to prepare and practise is by writing your answers down. Here's a quick example:
Describe a recent journey.
I’m going to talk about a recent journey to London. It was a couple of weekends ago, and I decided to visit the capital with some friends. I had never been before, so I wanted to go there to do some sightseeing. I don’t have a car, but my friend does, so he volunteered to drive. He had done the trip a few times before, so he knew the way. Maybe it was a bad idea to travel by car because the traffic between Manchester and London was terrible. We spent a lot of time sitting in traffic jams, which were due to roadworks and minor accidents, and it took us the best part of an afternoon to get there...
The description above is easy to understand, but it contains enough 'less common vocabulary' (underlined) to impress the examiner.