In America, the most common location for property investments is Florida, particularly on the Gulf Coast, around the cities of Tampa, Clearwater and St Petersburg. Other popular areas include Naples and around Orlando (popular mostly for rental properties, due to the proximity to Disneyland and other attractions).
Most foreign property sale companies can give you an information pack to give you background information on the property, however, be careful when viewing the property. If you are opting for a new build, you will probably be taken around a show home. 
Here, you will be presented with a list of optional extras, which you may assume come as standard. The list can be very long, and naturally the realtor (estate agent) will try and sell as many options as possible in order to earn a higher commission. Realtors in Florida are highly trained to work out your mood, and many get psychological training to try and sell in every possible scenario, and to judge your mood and adjust their selling practices accordingly! The tactic will probably be to get you to consider the resale value of the property, building on most people's lack of local knowledge to push them into buying extras which serve little purpose beyond a bigger commission cheque.
It is also important to deal with one agent, who is legally bound to tell you of all information that could affect a property, whereas if you purchase from the vending agent they are legally unable to tell you. For example, if the seller of the house wants a quick sale for financial reasons, and would accept a lower price than advertised, then the realtor cannot tell you. Indeed, anything which could be detrimental to the seller cannot be disclosed to you. Thus, if you buy through the seller's agent, you lose valuable legal rights and the realtor gains a much higher commission.
As a result, it is wise to select an agent that has an understanding of the differences between the property selling process in the USA and the UK, as they carry significant implications, and there are several significant differences.
When actually buying the house, the minimum deposit on a house in the USA is 20%, though this can vary up to 35%. Generally, a higher deposit will result in a lower mortgage interest rate. US mortgages are normally for a fixed period of 5, 15 or 30 year terms. Some UK banks will give a UK Sterling mortgage which can be converted to dollars at the time of purchase, reducing certain currency conversion risks.
The best advice when buying a property in the USA is simply to get an experienced agent who understands the differences between the UK and US markets, otherwise there are a number of traps and shortfalls for you to fall into.