Getting into Bangkok from the airport:
metered taxi should be around 400bht a bit more to khaosan
Where to go first?
The vast majoriy of people will head to either Khaosan road, or Sukhumvit/Nana. The former is where all the backpackers/travellers go. And the latter is the main bar-girl/gogo district which is where to go for the nightlife. Personally I hated Khaosan road. But different strokes for different folks and all that...
Accomodation:
You can get reasonable hotel rooms from just 700 baht (£12). I didnt stay in a hotel but decent hostel/'flashpackers' are around 400 for aircon and hot shower. Can get much cheaper hostels but no AC or hot shower. around 200
Getting around:
walk, you see much more, tuk tuks or local bus, also the skytrain. you can get a free ride in the tuk tuks if you stop at 3 places like gem stores, or suit shops. when they ask questions, just ask them back at them and have fun with them.
Money:
My nationwide card didnt charge me at all. I averaged £20 a day for everything. With this i lived like a king for 3 months. 3 meals a day, diving courses, trips etc
Law:
I walked around with my top off in swimming shorts. Nothing said. Most of the time i had a tshirt on though.
Be polite and respectful to police/authorities. This goes for anywhere i suppose, just dont **** them off. I hear the bangkok hitlon isnt a nice place
Girls:
Play safe kids.

This also means that when you are wasted check the luggage area before kissing
Food:
Do NOT avoid the street venders, i ate off them for 6 days in a row. The chicken pad thai on khosan road is 20p, is massive, good for you and filling. It will take you a few days to get used to food but then you will be fine. Mcdonalds and all the usual crap is also there. I highly recommend the fresh shrimp off the street vendors. Just make sure the fire is roasting hot first
Small local restaurants are also great. In sukumvit (sp) i ate a few local restaurants that were owned by thai families. great fun, great food, great memories. Meal is around 100bht (less that £2 when i went) for something like fresh noodles/rice and meat. Large beer was about 50
What to see?
Loads of stuff, but try and do less touristy things. Sure temples are great but when u have seen 5 they get boring. I walked into a political demonstration and it was great fun. Free food (black jelly stuff??) music and dancing. It was something to do with the presidend at the times of the riots were streets were blocked off by police but it was peaceful demonstration and was great
Finally, When you get home...
Save money to go back to thailand