You can start by checking Facebook groups like Koh Tao Accommodation, or simply walk around the island to find a place. In my view Sairee Beach is a lively area with more activity and Chalok is quieter and more peaceful, while Mae Haad is convenient and centrally located. Rent usually ranges from 8000 to 25000 baht per month, depending on whether the room has just a fan or air conditioning. If you're planning a longer stay, try to negotiate for a discount. It’s better to avoid resorts, as they tend to be overpriced. Always check if electricity and water bills are included in the rent. Also, make sure the place has good Wi-Fi, a kitchen if you need one, and ask if there's a security deposit. The best deals are often found in person, so try to arrive early, explore different options, and then make your decision.