As with any phone interview, just be confident, calm and relaxed. Make sure you know what you’re talking about, and don’t come across as too cocky or arrogant because most employers are not looking for this at all.
As usual, research the company in case they ask you any questions to try and trick you out, and don’t be tempted to try and make things up in an attempt to ‘have a go’ at impressing them.
Good luck!