Formal- How do you do?
Informal- What's up?

Formal- Firstly...
Informal- To start with...

Formal- Give my regards to...
Informal- Say hello to...

Formal- How do you do?
Informal- What's up?

Formal- Please state your business.
Informal- How may I help you?

Formal- One grows weary in these matters.
Informal- I'm getting tired of this junk.