How can you divide verbs into conjugation groups easily?


I have been learning the verb list for the N4 exam but I do not know how to
tell the group of a verb. Until now I have memorized them by heart.
Nevertheless I still have trouble telling the group of a verb because I can't
memorize them all. I wondered whether there is a systematic method of knowing
the group of a verb. Could you help me with that?

According to my textbook:

  * いきます belongs to group I
  * ねます belongs to group II
  * きます belongs to group III




First, Group III is the easiest to devide because 来{く}る and する are the only
verbs that belong to it. These verbs have each irregular conjugation as you
probably know.  

* * *

Then, if the verb ends with another than ''る'', it belongs to Group I.  
For example, you can tell which group 行{い}く belongs to, because it ends with
''く'' which is another than ''る''. Yes, ''行く'' belongs to Group I.  

* * *

Next, I'll tell about verbs that end with ''る''.  
You have to care the previous vowel to ''る''.  
For example, let's watch a verb ''乗{の}る''. This verb can be written ''noru''
in the alphabet, then the previous vowel to ''る'' is ''o''.  
If the previous vowel is '' _a_ '', '' _u_ '', or '' _o_ '', the verb belongs
to Group I.  

* * *

It's a difficult case for you when the verb ends with ''る'' and the previous
vowel to ''る'' is '' _-i_ '' or '' _-e_ '', e.g. 走{はし}る hash _iru_ , 食{た}べる
tab _eru_ , and 寝{ね}る n _eru_.  
Most verbs that end with ''i-る'' or ''e-る'' belong to Group II, so it's easier
to memorize verbs that belong to Group I in spite of its feature.  
  

It has been said by rhyaeris, I will mention them again.  
The verbs as follows are Group I, however you can't tell which group they
belong to only by their dictionary forms.  
I dare to give all verbs that I can remember, so there would be some
unfamiliar verbs for you.  
  
- 走{はし}る  
- 入{はい}る  
- 要{い}る いる{LH} (居{い}る belongs to Group II. いる{LH})   
- 煎{い}る いる{HL}  
- 帰{かえ}る かえる{HLL} (変{か}える belongs to Group II. かえる{LHH})  
- しゃべる (It is similar to 食{た}べる, but they belong to another group each other.)  
- 滑{すべ}る  
- 減{へ}る へる{LH} (経{へ}る belongs to Group II. へる{HL})  
- 知{し}る  
- 切{き}る きる{HL} (着{き}る belongs to Group II. きる{LH})  
- 散{ち}る  
- 蹴{け}る  
- 練{ね}る ねる{HL} (寝{ね}る belongs to Group II. ねる{LH})  
- 限{かぎ}る  
- 交{ま}じる/混{ま}じる (It's the intransitive verb of 交ぜる/混ぜる that belongs to Group II.)   
- 過{よ}ぎる (It has a little similar meaning to 過ぎる and すぎる and よぎる is written in the same kanji, however the two belong to different group from each other.)  
- 焦{あせ}る  
- 競{せ}る  
- 照{て}る  
- 火照{ほて}る  
- かじる  
- 茂{しげ}る  
- いじる  
- いびる  
- なじる  
- うねる  
- くねる (It is usually seen in ''曲がりくねる'')

Memorizing these verbs, you can tell that 走{はし}ります and 走{はし}った are correct,
not *走{はし}ます and *走{はし}た, 食{た}べます and 食{た}べた are correct not *食{た}べります and
*食{た}べった because 食べる isn't in the list above though it ends '' _e-る_ ''.

