Yes, if this is your first visit to Tobago, then I really think that a guided tour is by far the best thing to do. It will help you to find your feet and understand the layout of the island. It’s only a small island, so a full-day tour will really put everything into perspective, teach you a lot about the island, allow you to become more accustomed with the roads and driving style and generally feel more competent and confident to wander about on your own.
As regards recommendations of a good tour guide, I must confess I’m biased. I am always biased by good service from friendly people at a reasonable rate and who drive safely (this seems to be a rarity on Tobago). There is only one real contender in my books and experience – Yes Tourism
. Check out their website which details various standard tours that they offer. Also, search the forum - you will find lots of endorsement for their services.
You can also hire your car through Yes Tourism. They offer a car rental brokerage. In other words, they don’t own the cars themselves; they place your reservation with the best, most reliable car rental firms on Tobago. Their choice of rentals companies range from the very largest firms on the island, to some of the smaller, local operations. It costs no more than booking direct. I’ve used three of the firms they use and know they’re amongst the best and most reliable on the island.