Hi. I am currently in the process of exporting my girl to Australia- not sure if the same process applies but just thought I would mention quickly what I have done.
1. I have found using a brokerage has helped no end. They arrange the flight, approved crate and advise of a schedule for vet checks etc. Are you aware of the regulations for Mexico?
2. Contact DEFRA for an export health certificate- they will send this to your closest approved vet surgery ready to have tests done.
3. Contact the quarantine/governement body that issues Import permits- you might need one of these before you are allowed to book quarantine space.
4. Contact the quarantine centre in the country you are exporting to (MEX) and book a place (some quarantine places get booked out very quickly).
5. Once your vet has received the info from DEFRA they can carry out any tests/injections/worming etc etc that need to be done.
I hope some of this is relevant! If you are completely new to exporting I would put some feelers out to export brokers, even just to get some free info out of them! The DEFRA website may also be helpful.
Kate.