Keep a vest and a fist aid kit within reach, under the seat might not do it because you'd have to get off the bike in order to put on the vest. I keep mine in my tank bag. Keep your headlights on at all times in all countries. Some countries collect tolls for certain roads (motorways) and for some, like Austria, you don't 'pay as you go' at a toll station but need to purchase a vignette beforehand. Make sure to have one your windshield if necessary, otherwise it'll get ridiculously expensive.
"Life is not a journey to the grave with the intention of arriving safely in one pretty and well preserved piece, but to skid across the line broadside, thoroughly used up, worn out, leaking oil, shouting GERONIMO!"