Looking for tips for Bangkok?

Hi, I am going with my girlfriend to Thailand for the first 2 weeks in July. I am currently working on our travelling plans. I was wondering what we could do in 2-3 days in Bangkok? What shouldn't we miss to see? What sights are worth to go to? Which restaurants would you recommend? How is nightlife? Any nightclubs or coctail bars worth visiting? How should we move around Bangkok? Would you recommend booking a organizied citiy tour? If yes, where should I book one?