Cisco Switch: How To Check The Stacking Order Of The 3750-X Switches AND How To Manipulate It

I personally recommend you set the switch order that you want.  You can do like most people and just connect everything together and boot up the switches in the order you want them in, but I recommend a different way.  I say this because it doesn't always work out the way you want it to.  I did come across a stack of 6 3750-X switches that switch 3 and 4 were swapped.  Not because they were not connected up right, but because the switch stack determined it to be that way.
First, see the video below.  This is the easiest way to check the stacking order.  First, press the 'Mode' button 3 times.  You want the 'stack' LED lit up.

Now, how do you change that order if you need to?  See below.  I have the original config of those 6 I told you about earlier.  Switch 3 and 4 did not come up right in the order I wanted them to.
Switch#sh switch
Switch/Stack Mac Address : 10f3.11cb.0700
                                           H/W   Current
Switch#  Role   Mac Address     Priority Version  State
----------------------------------------------------------
*1       Master 10f3.11cb.0700     1      3       Ready
 2       Member 7cad.7494.7a80     1      3       Ready
 3       Member 7cad.7472.9b00     1      3       Ready
 4       Member 7cad.748a.b300     1      3       Ready
 5       Member 10f3.11cc.c980     1      3       Ready
 6       Member 7cad.7472.a080     1      3       Ready

I need to reverse these two.
Switch(config)#switch 3 renumber 4
WARNING: Changing the switch number may result in a
configuration change for that switch.
The interface configuration associated with the old switch
number will remain as a provisioned configuration.
Do you want to continue?[confirm]
Switch(config)#switch 4 ren 3
WARNING: Changing the switch number may result in a
configuration change for that switch.
The interface configuration associated with the old switch
number will remain as a provisioned configuration.
Do you want to continue?[confirm]
Changing Switch Number 4 to Switch Number 3
New Switch Number will be effective after next reboot
Switch(config)#exit

Now, lets take a look.  Notice the MAC address of switch 3 and 4.
Switch#sh switch
Switch/Stack Mac Address : 10f3.11cb.0700
                                           H/W   Current
Switch#  Role   Mac Address     Priority Version  State
----------------------------------------------------------
*1       Master 10f3.11cb.0700     15     3       Ready
 2       Member 7cad.7494.7a80     10     3       Ready
 3       Member 7cad.748a.b300     9      3       Ready
 4       Member 7cad.7472.9b00     8      3       Ready
 5       Member 10f3.11cc.c980     7      3       Ready
 6       Member 7cad.7472.a080     6      3       Ready

So now how do we also set the priority value for the switches?  Yes, I think you need to do this to make sure that your switches always come up in the proper switch placement that they are supposed to.
Notice the priority values that I have set for another stack:
Switch#show switch
Switch/Stack Mac Address : 10f3.11d1.6d00
                                           H/W   Current
Switch#  Role   Mac Address     Priority Version  State
----------------------------------------------------------
*1       Master 10f3.11d1.6d00     15     3       Ready
 2       Member 7cad.7472.a300     10     3       Ready
 3       Member 7cad.748a.a280     9      3       Ready
 4       Member 7cad.748a.a300     8      3       Ready
 5       Member 7cad.7494.5280     7      3       Ready

Notice a couple of things.  First, the * means that the switch is the master.  Second, the master switch is set to the highest priority (15).  Then, numerically the priority number goes down as the switch stack goes up.
Here is how you make these changes:
Switch(config)# switch 1 pri 15
Switch(config)# switch 2 pri 10
Switch(config)# switch 3 pri 9
Switch(config)# switch 4 pri 8
Switch(config)# switch 5 pri 7