I always play 4 minutes no add ons.
Anything longer allows players to 'muli-task' and you end
up playing a box. Same delay in between moves, no blunders
and no traps is a dead give away.
Not really seen it on here - why bother? No grade.
But other sites....I don't play there anymore.
A knowledge of opening traps, experience, instinct
and a quick tactical eye is the key.
(also don't dither on forced captures or obvious safety moves
(9.Bd2 & 13.Be2 in the game below).
Here is a typical blitz game of mine.
Black falls for an opening trick - I develop, push and poke.
Knowing where my pieces go by 'feel'.
Black's play starts to deteriorate in the last few moves as the clock takes it's toil.
All I am looking for in the end is the crucial mating pattern.
1.e4 e5 2.Nf3 d6 3.d4 Bg4 4.dxe5 dxe5 5.Qxd8+ Kxd8 6.Nxe5
Be6 7.Nc3 f6 8.Nf3 Bb4 9.Bd2 Nc6 10.O-O-O Ke7 11.a3 Bxc3
12.Bxc3 Bg4 13.Be2 Nh6 14.h3 Bxf3 15.Bxf3 Kf7 16.Bh5+ g6
17.Be2 Rhe8 18.Bc4+ Kg7 19.Rd7+ Re7 20.Rhd1 Rc8 21.g4
Kh8 22.g5 Ng8 23.gxf6 Rxd7 24.f7+ Nf6 25.Bxf6
Having said that I still find calculating odd on a monitor.
It's like playing chess on a postage stamp.