Here is the standard 'Bosch' relay. It is not always made by bosch, but it has their arrangment and numbering.
85 and 86 are hooked to the magnetic coil. If the relay has a diode to prevent voltage spikes the 12v In must face it to work properly.
 30 is to the battery and 87 is to the device, although installers sometimes reverse them.
 87a is on when the relay is off. It could turn on a burglar alarm, or a 'windows up' circuit when the ignition was off.
For more http://www.the12volt.com/

 Ford uses a cut out relay on their newer air conditioning. Sometimes it is their own brand of relay, but it equates to this drawing I figured out.
  You can see that most of the time the relay is off. When the AC is turned on Pin 10 tells the computer. When full throttle is used Pin 54 grounds the relay, turning it on. So actually, the computer thinks it is turning on something, not turning off!
  If something was connected to 87 it would come on at full throttle. A test lit a bulb at about 90 percent throttle or more.

  This is a GM vacuum switch. It was used on cars with an overdrive automatic and a carb to lock up the converter. When cruising there is vacuum, turning it on. When accelerating the vacuum dropped, turning it off.
  On the right is the truck type, which is on the firewall. The car type is way up by the drivers headlight for some reason, so you get lots of wire and vacuum hose.
  You can use this to turn off your AC, fans, or whatever.
I used it to examine when my EGR was turning on, and may use it to control my electric fan.

 These are some other bosch type relays. Oldsmobiles used Hella brand that have a plug with silicone seals top and bottom, and a locking tab. Classy.
 Older GMs used a plug filled with some nasty tar crap. A real mess to clean if you wanted to get the wires out.
  Next is an aftermarket bosch with a heat sensor that went on the rad hose. I used this for awhile with my second electric fan.

The first one is a bosch with a GM plug on the bottom.

 In the center is a GM patent relay. It uses different plugs and different numbers. It can take more juice, 30/40 amp, instead of the common 20/30 amp. On this one red is in, black is out, ground in between them. If there was an '87a' it would be top right.

 The Renault is neat because the plugs lock together side by side. The relays plug in with no lock at all.