
I have both imported and exported.
You need to decide if your going to let an agent do everything for you (you then put buyer in touch with them and they deal with all the export costs etc) and you only deal with the purchase of pup and any required vaccinations.
Airlines will vary, but the pup I sent out to the stud dog owner went at 11 weeks (a previous pup went in the cabin with the owners at 9 weeks) after her full puppy vaccinations even though they were not required).
If they go under 12 weeks they do not require Rabies vaccination, and she went without as in USA they usually do them later.
If you decide to do it alone then you will need to contact the airline Cargo section at the outgoing Airport and they can tell you exactly what to do, you do have to pay yourself.
With the most recent pup we took her to Heathrow ourselves paid what was required an the owner paid us within minutes by Paypal.
Previous exports I have had handled by Overhill Kennels and Exports, but we had timed things to coincide with picking up a friends new pup being imported that day.