Be sure to loosely buckle your seatbelt over your blanket so that flight attendants won't have to wake you to check that you're fastened in. If possible, choose a window seat. In a window seat you won't have to get up to let anyone out, and you will have only one person next to you. If you're lucky enough to find two empty seats together, take them. Grab a pillow and a blanket from the overhead bin and lay claim to them, then make yourself at home.
Sleep aids are a bad idea when flying.
It's hard to predict how pharmaceuticals will act in relation to jet lag and altitude changes. Another trick is to avoid alcohol, but if you choose to have a drink, order extra water. Set your mental alarm to go off before the landing announcement. This will give you time to wake up and freshen up before the plane touches down. The airline will be able to tell you if any tickets were canceled or changed, freeing a seat for you.