I believe TOEFL Preparation should be a complete exercise, and not part by part. After all, it is one’s command over the English language that we are talking about, and that would mean spoken, written, and all else. Having said that, let us see how the TOEFL Speaking Section can be faced the best.
Know what would be expected of you. Prepare yourself accordingly. You can gather some valuable tips on TOEFL Speaking Section from this link here.
It would be a good idea to enhance your vocabulary. However, adopting a fake accent can cause more embarrassment than good, so one would advise you to refrain from doing so. Just make sure your pronunciation is correct and clear, and you can also think of using some good English and even quotations, as and where applicable, if you can do it well. Here is some advice on using quotations in conversation, in case you wish to venture it.
The basic idea is to speak clearly, and with confidence. You need to have a good grammar for that. Please work towards it.
Reading good books, watching suitable English programmes on TV etc. can help.
Wish you the very best!