Bali is an interesting spot, accommodation wise it depends what you want. If you are young need alcohol and parties, you go to Kuta. Old and love massages food and doing nothing, they go to Sanur. First timers scared of Asians go to Nusa Dua, whilst rich and prepared to flaunt it will go to Jimbarin
The best diving locations are up the coast, away from everyone, and in little villages like amed.
What else to do, depends on where you are, but Ubud and the mountain, the volcano and the craft villages spring to mind. You will love Bali, there is so much culture to see, the old palaces, the dances and the music, alongside surf sand bikinis and good times
Give us a clue to what you like?