I guess it depends on if you want to be cheesy or original o.o
You could do it at a fancy dinner, or in a personal stroll through the park, or perhaps in a bathtub full of water and rose petals >>
Ooor do something else. Like go on a trip by yourselves to somewhere you both really enjoy/have really wanted to go to, or somewhere he really enjoys, and then do it there. Give him the perfect weekend full of fun and pampering, show him how much you love him before popping the big question. Leaving just small, subtle hints.