I used to love doing this on a Friday night when none of my friends seemed to be around. Rent a pile of horror or anime or cheesy old sci-fi, buy some special food (sandwich fixings, taco stuff or whatever) and settle in for a long night of scratching that B-movie itch.
I've done nights of 80s motor-horror mania with stuff like The Wraith and The Hitcher, a six-hour Star Blazers and salami sandwich marathon, classic 70s horror with the Shining, the Changeling, Don't Look Now, etc.
I haven't done that in two or three years. Since I've been married, I'm going to bed earlier and watching more variety.
However, two weekends ago, my wife got a last-minute invitation to a spontaneous girls' night in with her sisters. I was busy installing ductwork in the basement anyway, so she went to her sister's place for the night. What could I do but buy a lasagna and rent four of the more recent Godzilla movies?
So, I stayed up most of the night, then got up early to get some work done before she got home later in the morning. I was pretty much useless for the rest of the day, but it sure felt good.
I find the old "When Animals Attack" combo is fine - pick up a couple of friends, a handle of Captain Morgan's, and watch Anaconda and Congo back to back, followed by something that makes no sense whatsoever, like Fantasy Mission Force or Moulin Rouge or Buckaroo Banzai.
I do most of my b-movie watching on Friday and saturday nights, after my wife goes to bed. We usually watch a "regular" movie first. Then I dive into a few cheapo-selections after that.
I find that getting the most obscure movies that you know nothing about except what you see on the cover is a great way to find some new films. Recently I have been borrowing lots of Japanese Sci-fi [ish] and action films, like Princess Blade and the Returner. I liked them both, despite how shockingly silly they were.
It's always good for a surprise: the mystery movie has such a good appeal for me.