To start off, you will need a main image, which in this case is actually a Title (shameless self promotion). Although I made the text a slight off white, you can make it however you like.

Now you'll need a silhouette image of the main image to act as a mask (black is transparent,gray is semi-transparent, white is opaque). For this example, I made a copy of the above title/image, and then "stroked" it. Stroking is a Object Style modifier option in the Title Designer of Adobe Premier. All it basically did was fattened up the thickness of the text. Stroking is a personal preference, which will thicken the smoke effect some. The important thing is that the main image and silhouette image line up with each other.

You'll also need a smoke image. I'm assuming you know how to make a simple "clouds" image. If not, you can DL this one. Or better yet, check out my tutorial on Render Clouds to see how to expand upon this image.

In Adobe Premier, create a project with the main image, smoke image, and silhouette image. Put the main image on Video 2 and the silhouette image on Video 4, like shown. The idea is that the main image will pan across the screen in ten seconds. The smoke will start to appear at four seconds, and will last until 15 seconds.

Add a Gaussian Blur effect to the silhouette image and set the value to 15. (This is going to control how legible the text is.) Enable key framing (the clock like icon) then go to the last frame of the silhouette image on the timeline and set the Gaussian Blur to a higher value, I used the max value 50. When the smoky text appears, it will now be slightly blurred, and become more of a mass of smoke. Both the "stroke" applied to this image, and the blur will effect how legible the smoke will be.

Add the smoke image and line it up with the silhouette image in the timeline. Set its transparency key type to Track Matte. Add transparency key frames and adjust the transparency over time (red line) so that the smoke will fade in and out. Because track matte is being used, it should be noted that a transparency value of 0% should be avoided, and 1% should be considered the low value. This % value can be visualized by holding the shift key down while moving key frames.

Last, but not least, is the color adjustment on the smoke itself. This is done by adding a Tint video effect. What you'll actually be setting is the colors of the smoke image. This could be done directly in the smoke image itself, but this allows for finer control and easy adjustment, as well as the ability to use generic black and white images for effects (such as a library of cloud images like I have). Different effects could be easily achieved by switching which image to use.