Update August 2013
When travelling to Broadstairs I like to travel by train.
The opening of the High Speed Train (HST) to Broadstairs has now considerably shortened the travelling time to about one hour 20 minutes from over two hours previously, although it is more expensive than the slower options (£38:10 as of August 2013). The departure station for this service in London is St. Pancras International with a stop at Stratford International before heading for the country. The trains are comfortable and, oddly, have neither a first class section nor catering facilities so bring your own!
There are other slower and cheaper services should you prefer.
It's a shade under two hours from London Victoria via Rochester, with a half hourly service during the day and there is also a limited peak hour commuter service from London Charing Cross. The fare from Victoria is £31:90 as of August 2013.
The trains are all new and very comfortable, and there is a trolley buffet service on most daytime services on these slower routes.
The website provided is the very useful journey planner for all UK train journeys.
OK, so I "borrowed" the title for the tip from the company's own advertising but it really is appropriate for the shuttle bus service that operates around Thanet. It operates between Margate, Ramsgate Westwood Cross shopping centre and Broadstairs and with a weekday requency of about 10 minutes or less it is very reliable. It is not expensive and I recommend the Dayrider ticket which costs £2:80 (as of September 2011) which gives unlimited travel on the system for a day, as the name implies. If you have several trips to do, it represents great value.
If you are so inclined, some local people have even produced a Thanet Loop pubcrawl which I might have a go at some day.
I shall crosspost this tip in all my Thanet pages.
Catch the Thanet Loop bus from Queens Road, The High Street or The Broadway. One direction will take you to Margate, the other to Ramsgate for little more than £1. The trip takes about 15 minutes either way, and the buses go every 15 minutes during the day, every half hour in the evenings. Last bus to Margate (for the clubs) leaves Queens Rd at 11.30pm. You will have to get a taxi back.
There are three or four main taxi firms serving the Isle of Thanet (Margate, Broadstairs and Ramsgate). I have always found this firm to be reliable, with decent vehicles and polite drivers. They are always very prompt, as well.
As a guide, a trip from the Harbour area to the train station will be about £3.
I have shown the two main numbers below, although they have got a few.