Past Tense
To change most verbs into the past tense you just take off the -ar, -er, or -ir and conjugate them using the correct past tense chart.
The verb "ir" and "ser" are irregulars. They both conjugate the same way.
More irregulars...
-car, -gar, -zar verbs (irregular yo forms)
-car, -gar, -zar verbs (irregular yo forms)
Boot verbs-- only -ir verbs
These are called 'hotdog' verbs in the past tense because only the él/ella/ud. form and the ello/ella/uds. form.
(-ar or -er verbs that have boot verbs lose the change.)
e-ie stem changes become e-i
o-ue become o-u
Verbs with Irregular Stems