1Informal Present, Affirmative Verbs
Dictionary form
2Informal Present, Affirmative い-Adjectives
Dictionary form
3Informal Present, Affirmative な-Adjectives and Nouns
Adjective/noun + だ. You can drop the だ in spoken dialogue, but when writing it you'll want to include it.
4Informal Present, Negative る-Verbs
Drop る, add ない
5Informal Present, Negative う-Verbs
If it ends in う: Change う to わ, add ない
Otherwise: Change the final kana to the あ equivalent, add ない
6Informal Present, Negative する
しない
7Informal Present, Negative 来る
こない
8Informal Present, Negative ある
ない
9Informal Present, Negative い-Adjectives
Drop い, addくない
10Informal Present, Negative な-Adjectives/Nouns
Add じゃない
11Informal Forms
Informal form shows that you have some form of intimacy or seniority with the person you're speaking to. You typically use informal form with close friends, family members, children, and subordinates.
12Particles in Informal Conversation
Particles are often dropped in Japanese they're dropped A LOT in informal conversation. For instance, か isn't required to ask a question, and だ isn't necessary unless you're using a particle like よ or ね.
15Responding to a Question
While technically not wrong per se, you don't typically respond to a question with うん or ううん. You usually respond with the positive or negative form of the verb that the question ended with.
For example, if someone asks, "寿司食べる?" it's more natural to respond with, "うん、食べる。" or "食べる。" rather than just, "うん。"
16Informal + と思います
"I think..." You need to have the particle だ after nouns and な-adjectives.
17Informal Negative Verb + と思います
"I do not think..." By making the verb or adjective negative the sentence will literally translate to, "(Verb) did not happen I think"
18Informal + と言っていました
"They said..." This is used to say that someone said something and you were there to hear it.
If you weren't there to hear it, it's more appropriate to say と言いました
19Negative Verb + で + ください
"Please don't..."
20Informal (A) + のが + Describing A
Nominalization. You're using の to nominalize phrase A so that you can work with it like you would a noun. こと can often be used in place of の.
21が
A confusing particle that can be used in a few ways. Two ways the particle could be used are:
1. To add emphasis
2. Used with question words like 何, どこ, and どれ