BJT transistor matching
What to measure / match: hFEIB = base current
IC = collector current
hFE = DC current gain = IC / IB
The specs of a transistor (including hFE) varies with current draw, temperature, applied voltage, ... so if you want to be precise you should measure under the circumstances the transistor will see in his working environment.
how close to match the hFE values
time to settle
Don't become obsessed about matching, I've build my PPAs without having any transistor matched and they are working fine. Probably you can measure the difference but it is unlikely that you can hear the difference.
Furthermore you probably won't find matching pairs among the output transistors anyway. Just pick all transistors from a single order, they should come from a single manufacturing batch. Only when you are going to pick transistors from several orders (and several shops) matching should make a significant difference
When you have complementary pairs of different value, choose the high hFE pair over the middle and low pairs.
the easy way: using a DMMThis is the easiest, fastest and most simple way: use a digital multi meter (DMM) that sports a hFE mode. Just put the transistor to the supplied socket, select hFE mode and read the value on the display. The DMM calculates the hFE for IB being a fraction of a mA but that's precise enough for most applications.
deviations between DMMs
simple grouping by collector voltagejust measure the collector voltage and group the transistors by their voltage without calculating the hfe (easy + fast)
calculating hFEextensive and time-consuming, you need to measure two voltages and calculate the hFE values via a spreadsheet
VRB = voltage across base resistor
hFE = IC / IB
please note that you have to reverse the polarity when switching from npn to pnp transistors and that there is the risk of cooking the transistor when you connect it in a wrong way. Double check the pinout of the transistor (refer to datasheet!) and your wiring before applying voltage.