In this lesson I'm going to go over both the polite and plain forms of the present tense of verbs.
Before I start explaining how to conjugate verbs, I will point out some basics of verbs. There are three groups of verbs in Japanese: verbs that end in the vowel sound う i.e. あう, きく, and ころす; verbs that end with the sound of いる or える i.e. たべる, たりる, and いる; and three irregular verbs. From here on, I'm going to call the verbs ending with the vowel sound う "Group 1" and call the verbs ending with the sound of いる or える "Group 2". One note with verbs that end in いる or える, they can be a part of either Group 1 or Group 2.
Because Japanese does not have a future tense, the present tense serves as both a present tense and a future tense. When reading a verb in Japanese, you have to guess which it is off of the context.
I'm now going to explain the difference between the politeness levels of verbs then we'll move on to the conjugations. In Japanese, there are 3 levels of politeness of verbs: the honorific and humble forms, the polite form, and the plain form. I'm going to skip the honorific and humble forms because they aren't very useful at this level and just explain the polite and plain forms. The polite form is used around strangers. The plain form is normally used with friends and family or speaking to someone who is of a lower social rank.
The plain present tense is the same as the dictionary form which is the form you find in the dictionary and the form I list here.
The polite present tense is sometime called the ます form because when you finish conjugating the verb it ends in ます. The first step to conjugating a verb into the polite present tense is to conjugate it into it's ます-Stem then add ます to the end of the verb. I'm going to first explain how to conjugate Groups 1 and 2 verbs then show how to conjugate the irregular verbs.
For Verb Group 1, you take the final kana and change the う into an い i.e. あう→あい, きく→きき, and ころす→ころし. This form is the ます-Stem for Verb Group 1 verbs. After conjugating the verb into the ます-Stem you just add ます to the end of the stem to get the polite present tense of a Verb Group i.e. あい→あいます, きき→ききます, and ころし→ころします.
Verb Groups 2 verbs are a bit easier to conjugate. To conjugate one in it's ます-Stem, you just have to remove the final る from the verb i.e. たべる→たべ, たりる→たり, and いる→い. Now just take the ます-Stem and add ます to it i.e. たべ→たべます, たり→たります, and い→います.
I'll first list all of the irregular verbs then show you how to conjugate each of them. There is the irregular copula だ (to be) and the irregular verbs する and 来る (くる To come). だ, because it's not a normal verb, does not have a ます-Stem and conjugates straight into です for it's polite present tense. For する and 来る, Their ます-Stems are し and 来 (き) respectively. To get their polite present tense add ます to the end verb i.e. し→します and 来→来ます (きます).
Before I bring this lesson to a conclusion, I have one thing to say: do not forget how to conjugate into the ます-Stem because it will be useful later. With that said, this lesson is over, but if you need some practice conjugating verbs you can find some exercises here.
John