Negative Verbs (Casual Form)

There are simple rules for conjugating plain verbs into their negative form, based on their type.

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

Ta-da! That's it for the rules! It's just that simple. ある isn't usually an exception like the other two, it just happens to be in this case.

With this in mind, I'm going to conjugate some random verbs into their negative form for practice.

死ぬ  -  死なない
分かる  -  分からない
知る  -  知らない
食べる  -  食べない
泳ぐ  -  泳がない
読む  -  読まない
買う  -  買わない
話す  -  話さない
飲む  -  飲まない
いる  -  いない
走る  -  走らない
学ぶ  -  学ばない
遊ぶ  -  遊ばない
出る  -  出ない

It's important to note that 知る and 走る are godan verbs, despite the いる ending sounds. There are several other exceptions that I'll have to note as I continue to learn.

Credit goes to Tae Kim's lesson seen here.