As far as targeting goes, the range of options is growing but more limited than with banners, for several reasons.
But first, let's review your options:
Demo: This is the most common form of video targeting. With the dramatic expansion in the number of consumer plays available, it is now possible to effectively target most demos and gather significant inventory for the job. This is great news because in the past online video was chiefly used to reach the young and affluent.
Daypart: Daypart targeting is widely available.
Context: Some measure of contextual targeting is available, through site selection as well as by specific videos. Inventory for video specific targeting remains limited, and the narrower the context you seek, the less inventory will be available. Still, it's a good option to explore -- if you don't ask, you don't get.
Behavioral: Fairly uncommon so far, BT video is now available in fairly limited quantities. The chief reason for these low levels of inventory is that BT is chiefly managed through cookies, and pre-roll video cannot bear a cookie. But companion ads and some in banner ads can carry cookies, so expect more of this in the future.
One question that constantly gets asked is whether it is possible to avoid pairing marketing messages with news stories that will serve to harm brands. For example, an airline would not wish to have its ad on a plane crash video. This is fairly difficult to do with 100% certainty, though you can target an ad to a specific "channel" of a news site that has a very low likelihood of offering deleterious content.
Thanks for reading, and don't forget to write.