This is generally good advice but won't solve the problem of "ghost voltage" measurements. High input impedance is, for most purposes, a desirable characteristic in a meter to keep from loading the circuit under test. However, low impedance is needed to determine whether a power circuit is really energized or just capacitively coupled to an adjoining wire. This is one job where a relatively inexpensive electrical tester can outperform an expensive meter. (I am not talking about the $2.99 Harbor Freight meter here, but testers such as Klein's Wiggy, Ideal's Vol-Con, or Fluke's 7-600.)