I'm assuming you have a bulleted list of text on a slide. Select the placeholder that contains the text (In 2007, the placeholder will look like a dashed line. Click anywhere on the dashed line so it will look like a solid line).
Go to the "Animations" tab.
In the Animations Group choose "custom animation"
In the animation pane go to "Add Effect" and then "Entrance" and choose an effect. A typical effect to choose would be "Fly In"
This will make your bullets come in one at a time.
As to bolding, you could bold the text on the bullets themselves and not bold the others. I'm not sure if you simply want that or sometimes people want the current bullet in black and the others to dim to grey. If that's what you want, select the animation you just created in the animation pane. On the right of it you'll see a drop down arrow. Click that and go to "Effect Options".
On the "Effect" tab, go to "After Animation" and replace "Don't Dim" with the color you want bulleted text to change to after a new bullet is brought in.