its easier to put them through with your normal stuff, they go through separate if they are in a separate bag but count towards your 20kg or if no hand luggage most airlines take them as the 5kg of hand luggage you are allowed but still put them through so you are not lugging them around in departures, if they will go in your case put them in
I always find that the easiest way to transport them and to save any hassle at customs is just to wear them for the flight- as long as you unbuckle them on the plane they stay quite comfortable.