Accepting and declining
Answers to a request, suggestion or invitation: yes, an eager yes, and the soft no.
ii yo
polite ii desu yosure, it's fine
いいよ いいですよ
Grants a request or permission, or tells someone not to worry ('ii yo, ii yo').
ii yo, ashita iku.
Sure, I'll go tomorrow.
いいよ、明日行く。
ii desu yo, ashita ikimasu.
Sure, I'll go tomorrow.
いいですよ、明日行きます。
In reply to an offer, bare 'ii desu' (often with a hand wave) usually means 'no thanks'; in reply to 'kore de ii desu ka?' it means 'yes, that's fine'.
ii ne
polite ii desu nenice! sounds good
いいね いいですね
Welcomes a suggestion, or praises something someone shows or tells you.
ii ne, ashita ikou.
Nice, let's go tomorrow.
いいね、明日行こう。
ii desu ne, ashita ikimashou.
Sounds good, let's go tomorrow.
いいですね、明日行きましょう。
ii na (with na) is envy, 'lucky you / I wish', not approval.
chotto...
that's a bit... (no)
ちょっと… ちょっと
Declines politely: you trail off after chotto instead of saying no, and the listener fills in the refusal.
ashita wa chotto...
Tomorrow's not great...
明日はちょっと…
sumimasen, ashita wa chotto...
Sorry, tomorrow's a little difficult...
すみません、明日はちょっと…
Don't finish the sentence; trailing off is the refusal. When you hear it, take it as a no and don't ask why.