I took the morning 8AM ferry to havelock, the next day. There are three main ferry operators (government ferry, Makaruzz and Green ocean). The government ferry being the cheapest but it also takes the longest time. The other two are privately run ferries, so they area nicer and a bit better organised. I took Makaruzz and it was a pleasant experience. Its about an hour and a half's journey. The boats are clean and well organized. They also have a cafe inside where you can buy small eatables ablong the way. Makruzz also enables you to book your tickets online (only a month before the travel date). Even though you can reserve your ticket online, you are supposed to reach the dock 45 minutes before departure to check in. The makruzz ticket cost me 1100 bucks one way which is a shade expensive when compared to the other two ferry options. Also Makruzz, unlike green ocean, does not have an open deck to stand on. It is all indoor seating. You might want to book in advance during the peak season (December-January) since ferries are easily sold out.
Havelock is the main tourist island in the Andamans. It is a small island and you can pretty much visit all of it on a motorbike. It has three main beaches (Radhanagar, Elephant and Kalapatthar). Out of these, Radhanagar is by far the best. Infact radhanagar beach was voted the best beach in Asia by Time magazine. It is only accesible by motorbike or autorickshaw since its 20 Km away from beach number 3. Autorickshaw drivers will charge 800 bucks for a return trip. Radhanagar beach is a "must do." While I did not visit the other beaches, I would advise people to check out the other two. The elephant beach can either be reached by boat or by a 45 minute trek theough the jungle. So it would definitely be an experience and it is well known for water sports. Radhanagar beach is open till 5PM while the others close at 3:30PM. Also, BEWARE of snakes while at Radhanagar beach. The andamans are home to over 42 different species of snakes (Not trying to scare you guys :p).
I stayed at Barefoot scuba which is bacsically a five star scuba resort. It is located on beach number 3 which is where most of the accomodation on the island is located. You can stay at barefoot scuba only if you are diving/snorkeling on one of the days. Since I was traveling alone, I stayed in one of the frame huts which is the cheapest form of accomodation available. It was very basic, a bamboo hut with a matress and a wall fan. The room cost me 300 bucks a night. They have other forms of more luxurious accomodation available as well. For me, staying at budget places is the best way to interact with fellow travelers. I met loads of people because of my accommodation and diving.
There is minimal night life at Havelock. It gets really quiet by 9PM. Since I made a good bunch of friends, we would hang out till 10PM every night. We would buy our own booze from the one of the two liquor stores on the island (expect huge queues) and chill at a beach cafe called emerald gecko (Highly recommended for the food and the general vibe).
Note: Do try and carry your booze from Port Blair because havelock is very susceptible to alcohol shortages.