To order you can use:

per favore, mi dà ... ?

per favore, mi porta ....?

prendo ....

vorrei ....

There's no difference in these forms, they have the same meaning.

-Per favore, mi dà un panino e una spremuta di arancia?  Please could I have a toasted sandwich and an orange juice

-Ecco a lei   Here you are

-Quant'è?  How much is it?

-Quattro euro e cinquanta (€4.50)

-Ecco il resto  Here's your change