Do some research prehand and don't book or pay upfront. Unless you need it immediately or your hotel is really far away get a taxi there to start with. Then look into local hire companies and ask other tourists. There are always hidden costs but if you have not yet paid anything then you can go elsewhere if you find them unacceptable, something that you can't do if you have prepaid the basic hire cost. Bad experiences myself, maybe just unlucky but be careful.
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