Ordering:
I'd like to order...
Could I have...
Can I have ...
I'll have...
I'll order...
Recommending and asking for clarification:
What would you recommend?
What exactly is... ?
Offering:
What about ...?
How about ... ?
Would you like ... ?
Accepting:
Yes, I'd like that!
Yes, please!
Declining:
Thank you, but I prefer...
No, thank you.
Asking for the bill, thanking and responding:
Could/can I have the bill, please?
Thank you for an excellent meal!
Thank you for a lovely evening!
Don't mention it!
I enjoyed it very much, too!