There's a good chance that at some point in your undergraduate career, you will have to present a seminar: to stand in front of your fellow students and speak to them -- teach them -- about something. Many students find the prospect of giving a seminar intimidating, even terrifying. Most are not accustomed to public speaking. Some are shy or self-conscious when they're the centre of class attention. Some have been the victims of other students' seminars -- ill-organized, badly delivered, unenlightening -- and would rather not inflict such an ordeal on classmates.
Handled properly, however, the seminar can be a valuable learning experience. Many of you are destined to teach in the future, and undergraduate seminars can introduce you to a central part of the pedagogical trade. If you are going on to graduate school, you may as well get used to seminars; you could be on both the giving and the receiving ends of many of them!
Your ideals for your seminar should be the same as your ideals for good classroom presentations from your professors:
You should have gained a solid knowledge of your material through research. You should have thought about the material so as to develop your own ideas about it.
Your presentation should be clearly organized. It should be presented so as not to confuse or frustrate your classmates.
Your delivery should be fluent, not broken and halting, but also not breathlessly fast. You should try to engage your classmates to participate somehow, rather than to sit passively.
You should probably use some visual aids to help clarify and add visual interest to your oral delivery. Any visual aids you use should be neatly and clearly prepared.