You can hear it in your own voice. Agreeing to something in a meeting and the sentence comes out thin, half a tone higher, faster than the ones before it.
Misalignment announces itself in the body long before it reaches the level of argument. A tightening across the top of the chest. A reluctance to reread the email you have just sent.
Nobody is aligned all day, and nobody needs to be. But the signal is reliable and cheap to consult. When the voice goes thin, note what you just agreed to. That is your inventory of small betrayals, and they are almost all fixable while still small.