If you have a lot of time ( i.e. hours or days )
in which to prepare your topic, make sure you cover these stages:

• decide carefully on a favourite topic
  
• check out ideas, materials, resources
• prepare mind maps or spidergrams
• write notes as prompts if you need to
• rehearse your presentation with a friend
• do not under - or over run
• anticipate the questions the examiner may ask
• think about how you will respond to them

Practice
You have one-minute to prepare a short talk on one of these topics:

• Business English:
  "Advertising or marketing a new product or service"
• General English:
  "My closest friends"