I'm designing a device around a PIC18F4520 which will have 10 button 
inputs. The buttons are arcade-style large pushbuttons, and will be 
located at a moderate distance from the PIC (a few 10s of meters, most 
likely). The wires will probably run alongside other cabling - I don't 
know exactly what, but it will involve regular AC outlet power supplying 
a few incandescent light bulbs, among others. I don't expect any motors 
or other large inductive loads though.

What, if anything, should I add to the PIC's inputs to protect it from 
EMI, static, and the like? This is a one-off project, and minimum cost 
is not critical. I've been thinking about a bunch of optocouplers - 
these should nicely isolate the PIC from anything and everything on the 
outside, and I don't expect the LEDs to have any problems operating 
under these conditions. Any other ideas / suggestions?

Along similar lines, I need to run an RS232 link from a PC to the PIC. 
I'm using a MAX232 transceiver, as usual. Data rate isn't very high; 
9600baud should suffice. What would be the maximum length of the wiring 
under these conditions? Shielded vs. unshielded cabling, etc?
-- 
Hector Martin (hector@marcansoft.com)
Public Key: http://www.marcansoft.com/marcan.asc

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