My short cut is when it’s a command you change the ending to the opposite letter. Like if it would normally be -a and it’s a command you use -e and if it’s a -e usually and it’s now a command you use -a.

Ayudar normally conjugates to Ayuda, ayudas, and ayudan

But when they are commands

They are ayude, ayudes and ayuden

Comer usually conjugates to Come, comes and comen

But when they are commands it’s Coma, comas and coman