J is business class and Y is economy class. Within each class there are many subclasses. For example, J (and sometimes C) is full fare business, D is discounted business, I is really heavily discounted business class and U is Frequent Flyer award in business class. For the sake of discussion here, these are commonly just abbreviated as J (= business). There are about 10 or so subclasses in economy (eg Y B H K L M S O X etc). There is no logic behind the letter of the sub class and its relevance - ie it doesn't go A B C D E F etc according to price or fare.

In business, D is usually available for round world tickets and is very popular (and often restricted by airlines).

Do ask questions, the friendly group on this board usually help where possible!

For cheapest fares, try the on line agents such as expedia.com and others to get a feel for prices. If you can travel out of peak season, the fare will be less. Fares are based on departure date (so if you leave on the last day of the "cheap" season, you will be better off).

You cant book tickets until 11 months in advance (maybe 11.5 months). This saves potential mistakes in the booking process.