Be honest. Be yourself… just be the best version of yourself. There’s no point in making claims you can’t live up to but do ensure that you let your interviewer know your full skill-set. *HINT* Offer to give them a 5 minute potted history of yourself and finish with what you can bring to the table. It paves the way for a more open dialogue, and will show them how well you articulate and present yourself!
Listen carefully but don’t be scared to talk and don’t wait to be asked questions. Just make sure what you say is relevant and to the point.
Ask questions. If you’re not interested why should they be? If you have everything covered, just tell them that and ask if it would be OK to email them with anything further.
Body language is important, so be sure to make eye contact, and don’t slouch around – you need to look interested, engaged, and ready for action!
Always do your best. Even if this isn’t the job for you, it’s always nice to be offered, and you never know where this connection might lead.
BONUS TIP - Send a thank you. Manners cost nothing. (Well except that stamp in this instance!) People think it's old fashioned now so no-one really does it - if you do, you'll be remembered for it!