1. Asking about availability
More formal expressions:
Would it be possible to meet?
When would be convenient?
Less formal expressions:
Do you want to meet up?
When are you free?
2. Suggesting dates/times/places
More formal expressions:
Would Friday after dinner suit you?
Shall we meet in the lobby at 7.00?
Shall we say 8.30?
Are you doing anything on Tuesday?
Less formal expressions:
How about Friday evening after dinner?
How about (meeting in) the lobby at 7.00?
Would 8.30 be OK?
3. Accepting and refusing
More formal expressions:
That suits me.
(I'm afraid) I'm not free.
(I'm afraid) I have another engagement.
Less formal expressions:
That would be nice/fine (with me).
(I'm sorry) I can't make it then.
(I'm sorry) I've got something else on.
4. Confirming
More formal expressions:
So that's 7 o'clock on Wednesday, then.
I look forward to meeting you.
Less formal expressions:
See you on Tuesday, then.
Great. I look forward to it.