For the moment, let's assume you have a nicely structured speech planned out and focus on the all-important first impression. The first slide not only sets the tone for the rest of the presentation, it is also likely to be the slide that's on the screen when you introduce yourself. This is the moment when the audience decides if you're going to be an inspirational speaker worth listening to or yet another meatball in a suit likely to bore them to death.
For these reasons, getting the first slide right matters. Nothing beats a title slide that creates a visual connection between the presenter and the company or institution being represented. Using the corporate colors and company logo will help to reinforce the brand identity, but at the same time you don't want something that looks fussy or complicated. In short, the simpler, the better.
Let's assume you're presenting something on behalf of Peachpit. A quick peek Peachpit's Web site will let you determine the corporate colors and typefaces so you can re-create a similar look on your slides.
Keynote uses the standard OS X color picking tools, so you can grab colors from Web sites and other electronic documents easily. Open the Colors palette, and then click on the Magnifying Glass icon. Drag this to the color you're interested in (for example, on a Web page) and then click. This color will now appear on the topmost window of the Colors palette. If you want to store the color for later use, drag it from the window onto the tray of stored colors at the bottom of the palette (this is the row of small white boxes).
You can also add logos to the title slide. Simply drag a supported image file onto the slide window, and then resize as required. Keep logos nice and small though; the focus of this slide should always be the title of your talk.
One thing you don't need on this slide is your name. If your presenting skills are so poor that the audience can't even remember who you are, then you probably shouldn't be giving slideshow presentations at all! Besides, if people are engaged by your talk, they'll come and speak with you afterwards, at which point you can exchange business cards or journal reprints.
Figure 1: Aim for a balance between corporate colors, logos, text and empty space for your title slide. Keep it simple.