When should north begin with a capital letter?

Answer 1

It is capitalized at the beginning of the sentence or when it forms part of the proper noun

Examples:

North Asia

He headed north.

Another Answer

In my opinion, 'north' and 'south' should be capitalised whenever they refer to a location. For example, 'True North', 'True South', 'Magnetic North', and 'Magnetic South', are all locations and, so, should be capitalised.

On the other hand, magnetic polarities are not locations and should not be capitalised.

For example, "The magnetic polarity at Magnetic North is a south pole".

Answer 2

When it precedes a proper noun, ie; North London, North Kensington.

It would also be capitalised if used in 'northern' before a continent - even though "North America" is more appropriate - and only in front of state names which share a north and a south (Dakota, for instance should follow the proper noun rule.)

For countries don't capitalise northern France, or northern Finland, and, unless referring to a place such as Northern Ireland - which specifically uses that form as part of its title - northern should remain lower case. There are some countries which use North before their title: North Korea, for example.

If you are saying, "Let's drive north," for example, north is really like an adjective - a direction, also - so no capital is required.