The double meaning of Savoir

It's true that this isn't one of those grammar points that you'll cover as an essential part of A-level, but nevertheless once you get this it'll make the difference between being a student and sounding like a native.

'Savoir' we understand is the verb to know, as in "possessing knowledge about something", 

e.g

I know where to find the house

Je sais où trouver la maison 

However, the other meaning of savoir is "to know how to...". This is easy enough to grasp in English, when faced with translating a sentence such as "I know how to speak French" (Je sais parler français). But it is when in English we use the verb "to be able to" such as:

She is only four but already she can swim.     Would be:

Elle n'a que quatre ans mais déjà elle sait nager.

When faced with the question of 'should I use savoir?', I find that the easiest way is to replace 'can' with 'knows how to' and see if it makes sense in English. In which case, if it does, replace pouvoir with savoir.

This will make your French writing and speaking essentially more French, rather than being seen as an English person writing in French.