Micro switches generally have 3 connections; Common, Normally Open, Normally Closed. You should be connecting the Common and one of the other two, depending on whether you want the circuit to connect (NO) or disconnect (NC) when the button is pressed. Firmware can usually be configured to accommodate whichever state you choose.
@Bruce_Moore Ok, I want the circuit to connect when the button is pressed (which will be the always-on condition until the hotend hits the bed and the hinge rotates, disconnecting the circuit), which means Common+NO right?
Now about the design of the “hinge”, I have pretty much decided on a “snow plough”-type https://is.gd/Ey4moY- torsion spring (or even the clothes clamp type) to bring back the hinge into position. Do you guys have any experience embedding torsion springs into the printed plastic? Would the thin wires eat into the plastic fast?
https://is.gd/Ey4moY
Here’s an example of what I am thinking of:
(but this is quite off-topic for this post so i might spin this off to new post))
Wire the microswitch for NO or NC… Its easy to change the behavior inside Marlin Firmware to match the wired solution. If there is somethin that is not clear about the FW I can show where to find it.
I like the design and the idea. I belive that a optic sensor is even better than the cheap microswitch. With a optical switch the “blind” can the a M4 in the optical gap of the switch. Remove the plastic cover of the optical-switch and integrate the PCB into your design. This will give a nice connector. I also belive that this solution could be lighter and almost smaller.
This is the type of switch i suggest :
http://www.ebay.com/itm/A70-RAMPS-1-4-Optical-Endstop-Limit-Light-Control-Optical-Switch-3D-Printer-KG-/172364777088?hash=item2821bdc680:g:S14AAOSwLF1X9PYO
@Johnny_Linden Your suggestion is elegant and I would like to try it after I would have designed it first with what I have. I am not very sure that optical is that much better than mechanical -after all Atom 2.0 uses it 
- but it would certainly be better looking.
Prepare the wires to have 5V, GND and signal. I use servo-cables from R/C. The connector on poth ends are always 3 pin, but in the Microswitch solution I leave the 5V not connected. Switching from one sensor to another is done by reconnecting connector on the sensor side to match the actual sensor.
Ok, wiring microswitches aside, I have reverted the design to an easier -but again less elegant 
- compression spring loading for the hotend mount / lever:
The latest voron uses a switch for leveling, take a look