Ich will sounds demanding at a counter. German softens a request to ich möchte or, more politely still, ich hätte gerne, both of which are subjunctive forms. Könnten Sie works the same way when you are asking someone else to act.
Examples
- Ich hätte gerne eine Fahrkarte nach Köln.
- I would like a ticket to Cologne.
- Ich möchte erster Klasse fahren.
- I would like to travel first class.
- Könnten Sie mir sagen, wann der Zug abfährt?
- Could you tell me when the train leaves?
The mistake to avoid
Ich will is not rude in the way English want is, but it still sounds blunt in a shop.
Where this fits in
Travel & directions, German A2: Get around in a German-speaking city: take transport, ask the way, check into a hotel, and buy a ticket.