How can one calibrate a multimeter, like a UT61E or any other multimeter in the 50 ~200 $ pricemark, when one does NOT have an expensive FLUKE nor a friend who has a FLUKE)
Very generally and at the most basic, you need a precision voltage reference and resistors. Obtaining 0.1% is fairly easy, for resistors it's straightforward, and for voltage references look up "precision voltage reference" (something like this), and bias it with 0.1 to 1 mA.
The actual calibration procedure will vary from meter to meter, so you will need to dig up the appropriate documents.
Basically, there are lots of adjustable resistors on the multimeter PCB - don't forget to mark original positions of all of them before you start.
You ether get a precision resistor references (read datasheet on temperature coefficient), or find a guy with precision equipment in your city to compare the readings.