The previous posters have offered good advice. I have taken my 1.5 year-old Coton de Tulear, Avana, on six trips so far. Regarding airlines, you do need to reserve a spot in the cabin ahead of time. Some airlines only allow 3-5 dogs per flight. It's a pain but usually what I do is figure out my flights (be sure that you use the same airline if you have to make a connection), then I call up the airline to make sure there is room for the dog on that flight. Then I quickly book the flight, then I call to make the pet reservation. So far I've flown on Frontier, Alaska and three times on United. This Christmas we're flying on Southwest for the first time.
And it does help to get them acclimated to being in their crate before the trip. Since my dog was a puppy I've carried her around in a large Sturdibag (meets all airline size requirements and it's squishable). Sturdibag is a local company based out in Gig Harbor, WA. Whenever I go on a drive I take her in the Sturdibag (it has slots to loop the seatbelt through, so that the crate doesn't fall off the seat if you stop quick.) I take her to the grocery store and put the bag at the bottom of the cart and wheel her around. I take her in the bag to the dog park, etc. Get the doggie to associate going into the bag with good things, like treats and dog play time.
Pretty soon they won't mind being in the crate, and that will be a big help on a long flight.
best advice would be for the dog to be fed 8 hours previous to flight in order to avoid potty accidents. water is fine as long as he went to the bathroom 2 hours prior to flight