IBM 5160  -  Basics, for 5160 beginners

This is a slow computer.  BE PATIENT.  After turn-on, it can be minutes before an error message is displayed.
An AT-class keyboard will not work.  More information at here.
The IBM supplied floppy controller and 5.25" floppy drive are double density.  They will not read high density 5.25" floppies, such as 1.2M (2SHD) ones.
Just in case tried on a different computer, formatting or writing to a double density 5.25" floppy using a high density 5.25" drive is unreliable.  See here.
There is no 'CMOS SETUP'.  All motherboard configuration is done via switches/jumpers.
There is no real-time clock (RTC) on the motherboard or on IBM-supplied expansion cards.  Some examples of third-party solutions are at here.
Some of the securing screws for the drives are accessed via a well that is on the 5160's underside.  Photo at here.
After turning off the 5160's power supply, wait at least 1 second if you are planning to turn it back on.  Any shorter; the 5160 may not start.  See here.
The RAM test (and on-screen count) done by the motherboard's power-on self test (POST), excludes any expanded memory.  It does conventional memory only.
Expansion slot 8 is different to the other slots.  Most cards do not work in slot 8.  More information at here.
The 5160 motherboard does not have a keyboard controller chip.  Instead, it uses discrete components - see here.
The power-on self test (POST) of an IBM 5160 motherboard does not access floppy drive B: (if fitted).
The power-on self test (POST) of an IBM 5160 motherboard does not output POST codes that can be read by a POST card.  More information is at here.
The BASIC that is built into the motherboard, Cassette BASIC, cannot write/read BASIC programs to/from floppy disks (or hard disk drives).
The "Bytes free" figure that Cassette BASIC displays, is not the amount of fitted RAM.
Not all ISA expansion cards will work in an IBM 5160.  Ensure that any card you acquire is IBM 5160 compatible, and that it does not conflict with any existing card.
Aged tantalum capacitors are known to explode.  That has happened to me many times, particularly when I have acquired something that has not been powered on in years.  If the motherboard, or expansion cards, are exposed to your face when you power them on, then consider wearing eye protection.  More information at here.
If the 5160's IBM power supply (PSU) becomes overloaded, it will shut itself down, in order to protect itself.  If that occurs, the PSU will not generate any of the output DC voltages.  The PSU's cooling fan will still turn if the PSU powers it via AC mains voltage (rather than by DC voltage).

PSU overloading is typically caused by a short circuit in one of the many devices (motherboard, keyboard, expansion card, hard drive, floppy drive) that use power from the PSU.  In the IBM PC family, a tantalum capacitor is usually the culprit.

To be noted is that the 5160's IBM PSU requires a sufficient load in order to operate.  The 5160 motherboard alone is usually enough of a load.