3 way and 4 way switch wiring for residential lighting

I get many calls from home owners to either upgrade light switches to a more modern look or add some dimmers to their home’s lighting system.  I do that and all is well.
 
Some people try to do it themselves to save on the installation cost of an electrician and get frustrated when they change out the switches and they do not work properly.  So, if you are a “do it yourself” type, I suggest you shut off the electrical power at the fuse or breaker box first thing.  Then remove the switches from the electrical boxes but do not remove the wires from the switches.
 
I have collected a few schematics of 3 and 4 way switch wiring diagrams to help you understand how they function and how they are wired.  Look at these diagrams and then look at your switches until you feel you understand the wiring.  Here are the images.
 
 

Then go buy the proper switches and take off one wire at a time and put it in the same position on the new switch.  DO NOT take all the old switches off the wires and then try to figure out what wire goes where.  That is when confusion and frustration arise and then you must call me to clean up the situation, which I am happy to do.  I hope this is helpful to you DIY folks.  If you get in trouble, call me.