1. Ask him an 'identifying question' in order to ascertain that he is actually Sirius Black.
2. Once I'm certain it's truly him, I would welcome him in, then suggest a warm bath (or hot shower) in my humble tub. I would ask if he required my assistance.
3. I would offer to towel him dry, then give him my peignoir, robe (the long, comfy black one with the Klingon insignia on the lapel).
4. I would feed him, feed him so well he might consider staying a while. A long while.
5. Suggest a little wine, a little relaxaton and a movie. Dracula, perhaps.
6. Ask him if he likes it "doggy style".
7. In the morning, I would fix him a hearty breakfast, tell him he can keep the peignoir, robe (it Suits – Avocats sur Mesure him), and tell him he can come back anytime he likes.
8. Swear loudly when my alarm goes off and I realize it was all just a dream.
Ask him if he was in his Animagus form before he got here an just Lost his clothes. Let him climb in my one story house window, give him some of my brothers clothes. Hug him and ask him 10 million questions.
Take a picture of him then stand and laugh at him and then tell him stop being a pedo looking through my window and then tell him that i was upset when he died in harry potter :( :D