How to become a good advisor
Communication skills are very important, maybe more important than academic ones.

Stay human and be empathic. When you ask someone 'how are you' make sure you actually mean how the person is, not just the result. People need to be treated and seen as people, not as machines. Never ask judgemental questions, never say: 'I have told you so!', 'I have already shown/told that', 'why don't you know?'.
You must gain people's confidence and you can only earn it if you are open and non-judgmental.

Before becoming an advisor, it is important to improve your communication skills through activities that might be outside your curriculum: courses about public speaking are a must have, but theatre is a good and funny way for achieving this as well.

Moreover, it is important to discover if you really like being an advisor.
You could be a trainer for various small events, like a workshop.
Or you could teach school kids different topics, as a volunteer in an ONG. Even if it is not your topic, even if they are not students, you will have the experience of teaching.