Pack earplugs. Uncomfortable as they can be, wadding little bits of foam in your ears is far less annoying than being kept up all night by noise.
Bring eyeshades. They are for your eyes what earplugs are for your ears -- and they're especially important if your room doesn't have blackout curtains.
Bring your own sheets. If you have space to pack them, your own set of sheets could help you sleep better, as you're already used to their feel and scent. They also are helpful for folks with skin sensitivities who are worried about the detergents or bleach used to clean hotel linens.
Or at least bring your own pillowcase. If packing a whole extra set of sheets isn't an option, bring the pillowcase from your bed back home, to enjoy its worn-in feeling and familiar smell.
Spray your room. The chemicals used to clean hotel rooms or launder sheets can be a little overpowering. Add your own scent with a spritz or two of a gentle linen spray you bring from home.