How do you assign V and A1, etc. to target the tracks in CS4 PP?

The V1, a1 markers show up when you have a clip in the
source monitor window. They show where clips will default to if you use the insert or overlay tool on the source monitor window or the keyboard equivalent.

If you want to change them, click on the marker and slide it to another track and click in the track header to make that track active. Then you can insert from either the browser or the source monitor and the clip will land on the assigned track. It's a little confusing,I think, not as intutitive as it could be.

Audio tracks will self assign if the audio type you are placing is different from the track setup on the assigned track--- a mono clip will go to a different track if the assigned track is stereo, for example.

You can click and drag a clip to any video track regardless of whether it is active or not, assigned or not. The audio tends to find its own appropriate track...but you can move an audio clip from its default to any other audio track of the same type. / Battle Vaughan