Some pluses:
* A neat _play area_ (I don't care what the rest of your house looks like

)
* A clean bathroom (I will eventually have to go...

)
* A spacious table (room for everyone, including the DM, the dice, the books) -OR- an open/round seating area where everyone can clearly interact/communicate with everyone else.
* quiet enough to play (i LOVE kids and pets but if they make too much noise, the game gets distracted easily, even if only because the parent has to keep getting up to see what the child needs; that's not to say no kids or pets in the house, but if they are time-demanding kids or pets then they turn in to a distraction. Same goes for loud TVs in the other room or music that is too loud)
* safe neighborhood (i'm sorry, i just don't want to feel like i am going to get shot while walking from my street-parked car to your front door; or for that matter, i don't want to be worried the whole game that my car is going to get broken in to)
* Comfortable chairs -- my ass is skinny, i can feel every spring in a not-so-great chair/couch seat.

* drinks (even just talking water/whatever) - so a couple glasses or 2-liter are always nice pluses (but by no means a must-have)
Iffys:
* Food and snacks are real _maybes_ , it depends on who you are with. Some people have dietary restrictions (no pork or allergic to milk products makes something like pizza or choice or pizza toppings difficult) while others have preferences (i could eat chips but really, i'd rather have apples, etc) so someone may feel like the leper to not be part of the eating
But what it really comes down to is the people and the story:
Do I enjoy the company of the people?
Do I feel like a part of the group or just an add-on ?
Is the story/game entertaining?
Is the game flowing or is it constantly being interrupted?
etc
Wow, reading that back over, I sound like a jerk to play with

I mean, my tolerance is quite high so what I consider loud or spacious may be different than what others consider, so take what I said with a grain of salt.