They show that the audience is listening with interest. They should not be regarded as an attack on you, but as a collaborative search for deeper understanding. Be ready to get the discussion going after your presentation. Just in case nobody has anything to say, have some provocative questions or points for discussion ready to ask the group. It is very helpful to use visual aids in your presentation, as it helps people to understand.
People learn visually as well as orally.
Particularly if your accent is different from your audience's accent it can be very helpful to let them see your keywords. Overheads Overheads are the easiest and most reliable form of visual aids. You can use them as a prompt for your talk, so that you may not need cards. If you would like to learn more about it, you can follow the Webster's guide to PowerPoint, or ask the Computer Helpdesk for more information. Remember that PowerPoint may look great, but if the technology goes wrong you may be very embarrassed.