Ordering simply
“Tôi muốn…” means “I would like…”. You can use it before the name of a dish or drink. To ask whether there is a table for two, a useful phrase is “Có bàn cho hai người không?”
Drinks and preferences
For water, coffee or another drink, learn the product name and reuse a short sentence structure. If you have an allergy or dietary restriction, prepare a precise sentence and make sure it has been understood.
Asking for the bill
“Tính tiền” is a common expression for asking for the bill. Context and tone matter: keeping it simple, friendly and polite works in most situations.