I did mentioned in the past, some of the key advantages of using live view for image shoots. Nevertheless, as our focus now delve on video shooting, let me touch on some of the basic highlights on using it properly.
Focus is manual in live view video mode, in hope by Nikon that special video effects be possibly achieved at the cost of lazy users like us! But I am pleasantly surprised that sound recording (only mono channel recording) can be muted entirely (Shooting Menu -> Movie Settings). This gives us the ease of adding our music into the video composition thereafter. 720p HD video recording is limited to 5 minutes whereas a lower recording resolution will yields longer clips duration.
Interestingly, the White Balance can also be dynamically adjusted on the fly while recording your video on the Nikon D90! I am also quite impressed that the camera automatically adjust to the lowest ISO for your video shoot, depending on how fast a type of lens you have attached to your camera. Neat! Hence, the rule of thumb is, video quality significantly improves with a faster lens (ie bigger aperture). Note that for lens with aperture ring, it should be unlocked to allow manual adjustment for a proper video set.
Trick to try is this, if you are lazy about playing with your aperture during your video shoot, set it to the highest value for your lens and leave it as that, promising the deepest depth of field for sharper videos.