Remember, the law states that the person sitting with you when you practice must be at least 21 and have held a full licence for at least 3 years.
Start by practicing on quiet roads. You'll find it's better for your confidence, also, it's better for the person sitting with you.
When you have gained more experience - practice on as many different types of roads as possible and in all sorts of traffic conditions. The more driving you do, the better equipped you will be to deal with your test.