The only guaranteed early check-in of which I am aware is for Royal Ambassadors at Intercontinental hotels, and that status entails a referral or far more than "a few" stays. Like the poster above, I've been able to check in early at many hotels in other chains or independent hotels, but that's a function of availability and is unlikely if, for example, the hotel has been full the night before.
If it's that imperative, why don't you book the hotel for the night before?