From a technical perspective, the best way to use standby is not to use it. Amps that don't have standby do just fine, are better without it, actually.
Standby is a completely bizarre thing, as generally it's totally unnecessary. As such it may be likened to the human appendix, especially as it's 'one more thing to go wrong' and can cause nothing but trouble.
Generally it operates by interrupting the high tension (aka voltage) HT (aka B+ in North America) supply to the audio circuits. As such, it’s in the very highest voltage circuit in the amp, with very high current levels available. When actuated, voltage and current surges are created as current rushes into uncharged caps etc.
Flipping the mains power switch energises the whole power supply, it puts power to the tube heaters and to the HT used by the audio circuits. But with standby engaged (switch contacts open), the tubes heat up without the HT reaching the audio circuits. So the tubes warm up and become ready for use, but until standby is flipped and HT current flows to them, the audio circuits can't work.
Kinda like Igor in Frankenstein's laboratory, throwing that lever switch to kick the monster in life
Within the field of tube audio, there's no precedent for standby, no tube technical reference manuals or books call for its use or suggest that such an arrangement could be in any way beneficial; no tube audio equipment other than guitar amps have ever featured standby.
It is safe to say that if an amp has a tube rectifier, even if the invented concept (cathode stripping of receiving tubes) used to justify it was valid (which it isn't), there's no conceivable technical benefit in using standby, as tube rectifiers provide a delayed, slow, smooth ramp up of HT; with many amp designs, (hot switching type) standby causes extreme stress to tube rectifiers, shortens their operational life / promotes early, catastrophic failure (arcing inside the tube).
Standby seems to have come into being in order to enable Fender to use cheaper/more readily available, lower voltage HT caps in early, tweed era versions of the Bassman etc. Unfortunately it was retained when they later specified properly rated caps.
I guess it proved popular as a convenience feature with users, and perhaps they were familiar with using standby with tube radio communication transmitters from their time in military service.
The thing is, unlike transmitting tubes, receiving tubes (ie those used in guitar amps) don't require a HT standby.
I suspect another thing is that guys like the whole ritual thing about using standby, getting the double switching thing 'just so' is a bit reminiscent of getting the motor started in old Hammond organs, it requires the user to be 'in the know', and they like to play one upmanship and critique other guy's versions of the standby ritual ('Dude, you're getting it all wrong, you'll be wrecking your tubes!').
As with so many other aspects of guitar amp design, other manufacturers eventually copied the feature from Fender. Though it took Vox several decades to succumb to the marketing dept pressure ('all other professional grade tube amps have standby, not having it makes Vox look cheap').
Here's the technical 'ins and outs' about it
www.valvewizard.co.uk/standby.htmlApologies, I have a 'bee in my bonnet' about standby
FYI the switches used for standby are never rated adequately for the application; 250V switches are only ever used, yet the voltage on them is typically much higher, sometimes over 500V. But 250V switches are cheap, whereas switches with a higher voltage rating are far more expensive, and would generally be too big to fit in the space available.
