Ensure the Flt Deck know that there is a dog in the hold so that they heat it. I know it should be on the manifest but it is sometimes missed. Just a polite word with the cabin crew would suffice.
It won't just be on the manifest, it will be on the NOTOC as well, so no chance of the flightdeck not knowing there is AVI on board. (that said there are still certain imbeciles who try/do put AVI in the same hold as dry ice
)
If flying with BA, beware of them saying the animal crate is too small even though a vet says it's big enough. A good friend of mine had to accommodate herself and two cats in the US for a surprise extra night when moving countries because BA rejected one of the crates despite a vet specifying them as acceptable,
As has been said below, just because a vet says it is OK doesn't mean it fits IATA regulations. It may be OK to carry a dog to/from a vet surgery, but not suitable for an eight hour flight. The regs are very specific and I know when I did AVI checks they were always always as thorough as a DG check for instance.