Frankfurt is an interesting German city. Although English speakers normally refer to the city simply as "Frankfurt", the full name of the city is "Frankfurt am Main". The locals will often refer to this city of just under 3 million by its full name to distinguish it from another much smaller German city named Frankfurt which is situated on the Polish border. Frankfurt is a rather unique German city in that it first of all is the main financial centre within Europe, being home to the European Central Bank of euro fame. The Frankfurt Stock Exchange is well-known within the region, and the city mixes some of the old-town charm with modern-day high-rises and skyscrapers. The locals will often call the city "Mainhattan" which is a play on words for "Manhattan".
Frankfurt is an area that has a surprisingly large tourist industry. Because of that, the best time to travel to the area is basically on a year-round basis. There are some things to keep in mind, however. First of all, the summers are warmer than in the UK while winters are much colder. Frankfurt locals are usually very welcoming of visitors, including those of the English persuasion. Are you looking to get a good cultural feel of the city? If so, then the best time to travel would be either during February and March to take in the Carneval season or March through April to enjoy the internationally-known Dippemess Festival throughout the area.
Some important things to remember before you travel to the area would include the cost of living, which is actually lower than in the U.K. Another important tip to remember is that Frankfurt is actually serviced by two airports. The larger Frankfort Main Airport is closer to the city and more popular with well-off individuals, whereas Frankfurt Hahn Airport is used by budget carriers and is located about two hours from the city centre.
If you are looking for transport the the centre after arriving at Frankfurt Main Airport then you can board the local trains named S8, S9 or RE80. These trains will usually run about 15 minutes and will cost you around 4.50 euros to get to the centre of the city.
Accommodation generally will run you between 20 euro a person for hostels and 50 euros for hotels. Frankfurt has both a good public transportation system and a good taxi system. If you choose to do public transportation you should invest in a "Frankfurt Card" that will also give you offers for museums and other attractions. You can take the tram, S-Bahn, the underground line or a bus. You can also take a taxi, but these are generally more expensive and take longer.