Plain Form Verbs

I know I've learned these verb conjugations already, but I'm going to do a quick refresh here since they're used in my current chapter of Genki. I'm on Chapter 8 right now, so woohoo! Over halfway done!

Present, positive, plain verbs are simply the dictionary form of the verb. That's the original form with no conjugations. To change them into plain negative form, I do the following:

Ichidan Verbs:

• Drop the る and add ない.

Godan Verbs:

• If the verb ends in う 
• Change the う to わ and add ない
• If the verb ends in anything else
• Replace the u-sound with the a-equivalent and add ない

Exception Verbs:

• する - しない
• 来る - こない
• ある - ない

Plain form is used in a variety of grammatical constructs where polite form simply can't be used, so it's important to be comfortable with it.