I met a Dr at the open house in the department and was soo excited about his research interests,
he gave me his card and asked me to contact him, which do you think is better phoning and asking for an appointment or emailing?

and what should I mention ?

what exactly are you supposed to say?
what are the most common reasons for supervisors to turn down students ?

can everyone share their stories please about finding supervisors?

sorry but i'm realy nervous about it ! :$

This does feel a bit awkward, if i were you i would send a brief email outlining your interests, and state that you are aware of his area of expertise and you were wondering if he might have a look at your proposal to see if he would be interested in supervising your project. He'll either be flattered, or used to it. Don't worry

I would go for email too, just because you can outline your initial ideas coherently! I then met up with two potential supervisors, one in their university, the other in a mutually convenient library. If that's not reasonable then maybe call after some email contact, or the potential supervisor is cliely to suggest something!

I don't understand whether you're going for a Masters or a PhD since you haven't specified and unless you're going for an MRes..? But..

I think email is just best for time reasons, they can read it at their leisure and it means you don't have to make time during office hours during which they might not even be available. It also means you can get across what background you're coming from with a little more grace (I don't know about you but I get nervous on calls to superiors!) and intelligence and you can really think through what you want to say.

Mention where and when you met, but don't expect him to remember you since they're busy and network a lot (understandable), then I would go on to say that you're contacting him since he advised you to, say you'd like to meet up to discuss the possibility of doing a masters/PhD. Suggest a date within a few weeks time, then mention your availability in cse that date doesn't suit him.