The most common mistake in YouTube advertising is taking the promotional film you happen to have and running it as it is. In practice the format is decided by your objective, not by the video in hand, and the format then decides how the video should be built. Reverse that order and the budget goes on a film nobody watches to the end.
What each format is for
Skippable in-stream ads play before or during a video, and the viewer can skip after five seconds. There is no maximum length, though under three minutes is recommended. This is the main format for sales, leads and website traffic.
Non-skippable in-stream ads run 15 to 60 seconds and cannot be skipped. They work when the whole message has to be seen; the cost is the viewer's patience, which is why they belong to reach and awareness campaigns.
Bumper ads are six seconds or shorter and cannot be skipped. They exist to remind someone of one thing: a brand name, a date, an offer. Trying to fit a product explanation into a bumper results in explaining nothing in six seconds.
In-feed ads appear like a recommendation in search results, on the home feed and in the watch-next list, and the user clicks to watch — meaning interest has already been shown. Shorts ads appear in the vertical feed and can be skipped instantly with a swipe, which calls for vertical footage and an edit that still reads with the sound off.
The first five seconds
In the skippable format the viewer has a button after five seconds. That makes the first five seconds not an introduction but the entire advertisement. An opening animation of a logo spinning in space spends exactly the moment the viewer is deciding.
The order that works in practice: movement or a face in the first second, a clear sense of who you are speaking to by the second, and what you offer stated before the fifth. Everything after that is for the people who did not skip. Saving the brand name for the end is the same mistake in another form — anyone who skips never sees it.
Targeting: intent or audience?
YouTube offers targeting both by audience traits (interests, demographics) and by search intent. For most businesses the intent side is more efficient: reaching people who search particular topics or watch competing content lands closer to a result than reaching a broad interest group. Audience targeting earns its place in awareness campaigns and when reach has to grow.
Measurement: a view is not a purchase
The most visible number in a video campaign report is views, and it is also the most misleading. A view indicates interest; it is not an outcome. Making sure conversion tracking works before the campaign launches prevents the question "plenty of views, but what happened?" three months later. The effect of video advertising often shows up not in direct clicks but in later searches and direct visits, so reporting that looks only at last click makes video look worse than it is.
One video is not enough
Showing the same ad to the same person repeatedly eventually reverses the effect; the viewer remembers the brand, but not for a good reason. There are two ways round it: cap the frequency, and keep more than one edit in hand.
More than one edit does not mean shooting again from scratch. Short variants that open on a different angle from the same footage, start with a different line, or lead with a different offer are usually enough. Measuring which one holds, rather than guessing, is the fastest way to learn on the video side.
Budget and duration
Video campaigns need a longer warm-up than search ads. A campaign switched off after a few days is switched off before the system has learned who is interested. Running one format for long enough beats splitting the budget across several at once — it produces both a more readable result and less waste.