Tips on how to practice while confined to my bedroom?

I'm living with roommates for the first time, so my spiritual practices have to be confined to my tiny room or really subtle (I have a Japanese protection charm by the front door, but they think it's just decoration.) I can't use a lot of smoke since I can't open my window and I can't have it lingering in my room. I guess what I'm asking is how can I whittle my practice down but still remain effective? I only have a really tiny table for an alter.