First thing I do is give the house a thorough cleaning (which I did yesterday). That way I dont have to worry about cleaning while I am decorating and it leaves less of a mess at the end.
I then go thru my house and look for all the "stuff" ie: pictures, non-Christmas scented candles, bric-a-brac and whatnots that will be replaced with Christmas items. Collect all these and put into boxes I store in spare closets.
I am not sure where you store all of your decorations but I have mine in my shop and I have my tubs marked as to what is in them. I then only take in what I need at that time. Say if I want to put out my tabletop decorations I do that...and when I am finished the tub goes back out to the shop before I bring in another. Saves room and keeps me from getting overwhelmed.
The last thing I bring in is my Christmas tree decorations only because I do it last. The main thing I try to do is clean as I go so that I dont have empty boxes and tubs sitting around long after I have finished decorating.
Hallelujah! Holy S***! Where's the Tylenol?