2.- How to say it: Modal verbs (can/could/be able to).

To make requests and express possibility you need to use Modal Verbs like can and could. Remember that they are always followed by Infinitive without to:

When you want to make a request, you are going to use:

• Can
  • Can I have your name and email address, please?
• Could (if the request is more polite)
  • Could you tell me about it?

To express possibility, you are going to use:

• Can
  • You can change the way your company operates.
• Could (if it is a remote possibility)
  • You could find a better offer in another department store.

Apart from making requests and expressing possibility, there are more uses of can:

• Ability
  • We can speak English.
• Permission
  • You can't smoke here, but you can smoke in the garden.

If you want to express can in the past, you are going to use could:

• I could swim across that river when I was young.

But, if you want to express can in the future, you are going to use will be able to:

• I’ll (will) be able to travel on the second half of July.