Book your accomodation ASAP

ffransiska is right, it does depend where you want to go, what kind of accomodation you prefer and what your budget is. There is lots of variety and a lot to see.

The problem that you may have is that the two weeks over Christmas and New Year's week is very, very busy. A lot of the smaller hotels are already fully booked. I just booked last week and had to contact 5-6 hotels before I got one that had a room: and that was the last one they had! I'd advise you to spend as much time as you can this weekend looking at options on the Internet and then book something as soon as possible.

You can try these sites:
http://haystack.lonelyplanet.com/accommodation/Indonesia-Bali-R2504.html
http://www.balidiscovery.com

If you're keen to meet fellow travellers, Kuta is probably a good start (anywhere from Tuban near the airport through to Legian north of Kuta is within walking distance of many bars, cafes, clubs and shops).

Maps here:
http://mapsbali.com/areas/kuta.php

All the hotels and guesthouses will be very busy during the first week of January, as will be the beach, as will be the bars and clubs! There shouldn't be too difficult to meet people. Avoiding people might be more difficult!