Never had any bother in hotels.
I Just walk in like I'm a guest and head straight for the lifts or the stairs.
As said above, the trick is to get all the details before you walk in, what floor and what room number.
Don't need to look at reception, other guests or cleaners.
Don't look shifty.
If I ever got asked (which in all my years has not happened yet), I'd say I were visiting a friend, which is true, for the next hour she's going to be my best friend.