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What is independence?
There isn't really a single, accepted international definition of 'an independent country'. It is really a feature of three aspects – the legal right to enter into internationally-binding contracts, the recognition of the country by other countries and the perception of it being independent by all concerned.
How do you get the power to sign internationally-binding contracts?
You need what is called 'legal personality'. That can happen immediately after a referendum vote as it can be granted by the UK Government. This should be absolutely the first thing Scotland asks for so it can start building a new nation – it doesn't need to wait for 'independence day'.
So how do you know if you're independent?
Most people generally see membership of the United Nations as being the best indicator of being a recognised independent country.
How do you join the United Nations?
It's a four-stage process but the key bits are that you must get the support of nine of the 15 members of the Security Council and then two thirds of the General Assembly.
Is there any barrier to that for Scotland?
The key to this is a proper recognition agreement with the rest of the UK. As a member of the Security Council, if the UK voted to recognise Scotland it is almost certain there would be no major objections.
And is that it?
Well no, to function as an independent nation there is a lot more that needs to be done (like set up a full tax system so you can pay for the services a modern country needs to provide). And there are others international organisations we'd want to join quickly (like with the World Trade Organisation so we could trade with other countries feely). But basically yes, once you have legal personality and you're a member of the United Nations, everyone's perception will be that you are an independent country and so you'll be able to behave like one.