Money - Take a hundred dollar bills, Take about $1000 for a week, Make sure your bank knows your travel plans so you can use your ATM card. If you feel uncomfortable carrying so much money, take $300 and use your ATM for the rest.
Scams, when you get to the airport, go to the taxi rank to get a cab. Do not go with the drivers that come up to you after you exit passport control.
Cell Service - If you use AT&T or T-Mobile in the states, make sure your phone is unlocked and get a SIM card. You can get one at the airport or any 7-11. I use DTAC (Happy SIM). For Sprint SIM card will not work.
Hotels - Stay on or around Soi 4 (Nana Plaza) See the Hotel section on the Board for recommendations. Good Central location, and everything is accessible via Skytrain.
Transportation - Forget Uber and Taxis, too much traffic. Take the Skytrain. For sightseeing get a day pass on the river. Take the Skytrain to Saphan Taksin station, and the booth is right after you exit. Soi Cowboy is one stop from Nana on the Sktrain.