I guess it is important to be prepared for any kind of interviews, be it to be a cabin crew, a pilot or just a road sweeper. You have to be aware of the job scope, the pros and cons of the job and of course the pay.
1. Do a background check on the company. Research on their main operations and stuff like that. Just in case they asked you, ya know?
2. If you're a guy, trim your hair and look neat.
3. Teeth check.
4. Having an interview suit would do you good. Leave the blazer behind if you think it's too fancy. A shirt and a tie, with plain working pants. Stick to beige and black. As for the shirt, minimize on the patterns, pastel colour preferably and a plain tie.
5. Practise smiling.
6. On the interview date, there will be hundreds of candidates and among them could be potential 'spies'. Nonetheless, smile and be friendly if anyone should so approach you with some queries. Don't say 'Don't know' and looked away because you might just be deemed aloof.
Have some faith in yourself. If you believe you can do it, you will.