Don't try strategies like going to arrivals area at the airport to save money for taxis, it simply doesn't work, you are not smarter than them
Do oblige taxist to put taxy-meter, you will save a lot of money
Don't contract with pink taxis, those are the worst, yellow with brown strips are the ones
Do go to Wat Po, it's not Wat Phra kaew but it's even more worth it
Do have a Thai massage in Bangkok, it's cheap and 'safe'. I said Thai massage, not oil massage.
Don't eat bugs in Khao San road, neither Thai people do that
Do eat at Royal India in Chinatown, it is hidden but well worth it
Don't go to other commercial centre as Siam Paragon for shopping but go straight to MBK, it's the only really worth it
Do go after 6pm to see Bangkok skyline from Scirocco Sky Bar, but remember you don't need to buy cocktails, just pretend you are doing it. And presenting yourself with thai pants and shopping bags won't allow you to go up
Don't stay in the cocktail area in scirocco bar, go straight to the restaurant one for a better view
Don't ask selfies people to take pictures of you, they won't be able to do it
Don't take skytrain if you are in a group, taxi is way cheaper
Do take boat to go from Khao San road to Chinatown and Silom, the fastest and cheapest way (maybe not the safest)
Do go to eat in commercial centre but be aware, quality can be worst than street seller
Do enjoy Bangkok, it's chaos but it's really pleasant
Do contract on prices, do contract on prices, do contract on prices..!