It depends on the circumstances. If the person is a student and has to do presentations in class then a friend could help them rehearse, say starting 1:1 then building up slowly with a few more friends. If that person is naturally shy then there are exercises to go through that will help build self esteem.
Fear can be conquered by:
1. Having the speech or topic clearly written down on card or paper.
2. Rehearsing the speech or talk over to a small group of friends or famly.
3. Keeping positive thoughts in the mind...eg talk to one, talk to many.
4. Accepting that nerves are natural and most people have them.
5. Gradually building up confidence by taking small steps here and there - talk to a stranger in a store/shop, help someone.
6. Reassuring yourself that nothing can go wrong.