Stem Change Verbs In Spanish

These are verbs where the verb changes its stem.  Here are the steps to make it easier.

1. Identify the verb type-AR, ER and IR and then remove the ending.
2. Identify the vowel of the stem.
3. Change the vowel in the following way:

E>IE
E>I
O>UE
U>UE


This does not happen in the first and second person plural.
e.g. Pensar-To Think
Pienso            pensamos
Piensas           pensáis
Piensa             piensan