Things to consider

In case you wish to explore the island more in depth, especially on foot, get a copy of the more detailed, topographic fold-up map "Koh Tao in Focus" [the one with the clown fish cover], available for free in shops, resorts, dive centers and agencies

Some advice that matters not only in Koh Tao: 

Please keep in mind that you are a visitor and treat the locals and the environment with the necessary respect. Try to blend in rather than to stick out, your customs are not the standards here. For example: Thais are offended by nudity; decent clothing in religious sites is required; losing your temper means losing your face and gets you nowhere. 

Imagine how many visitors have been here already and how many of them might have misbehaved, naturally this reflects on the future ones. So always being friendly, polite and calm, keep smiling even when it seems difficult, will help a lot and open many doors. 

If you have a complaint try rather to explain than to demand, your needs are not necessarily understood.

When you feel wronged or cheated, consider if the cause is worth the hassle and maybe just follow the true Thai tradition of "Mai Pen Rai" meaning "Never mind"  ...and always keep smiling.

Attention, should you experience a serious problem or just be in the need of some assistance or advice, please contact the english speaking Tourist Police.

Even there are many streetlights in the main areas, there are still a lot of dark areas with uneven footing, best carry a decent flashlight and walking home with a friend is always a good idea.

Watch out for con-men running around & asking for dubious "donations". Better give your money to the legit Animal Clinic or support the school.

Oh, sorry it has to be said: drugs of any kind are illegal in Tao same anywhere else, there's undercover police, even a little joint is treated as a severe offence, may result in a financial disaster, a visa ban, or worse. There, you have been warned!