The last quarter is where a large share of the year's advertising money moves, and it is also where the least preparation happens, because everyone is busy running the campaigns they already have.
The work that decides how Q4 goes is done now, in the quiet weeks before it starts.
Test creatives while traffic is still cheap
Costs rise as more advertisers compete for the same inventory. Any testing you postpone gets done at peak prices, with less room for error.
Use the current period to build a rotation you trust. Entering the busy season with proven creatives is the single largest advantage available, and it is available only in advance.
Fix the technical work you have been avoiding
Page speed, mobile layout, tracking gaps, broken redirects, the landing page nobody has looked at since spring.
None of this is urgent in September. All of it becomes urgent in November, when traffic is expensive and every leak costs more per visitor than it did before.
Decide your budget structure now
Set what you will spend, what you will hold back and what result would make you stop. Decisions made calmly in advance are better than decisions made at three in the morning during a period where the numbers move fast.
Seasonal campaigns compress everything. Reaction time shortens, and pre-made rules are what protect you from your own improvisation.
Understand what shifts in your vertical
Not every vertical peaks in the same weeks, and the shopping calendar has several distinct moments with different behavior. A breakdown of how holiday advertising periods actually behave is more useful than a general assumption that Q4 is busy, because the differences between early November and late December are large enough to change what you run.
Check your cash position
Seasonal spending means fronting more money for longer while payment terms stay the same. If your budget is planned around normal cycles, a peak season can create a shortage even while performance is good.
Work out what you can front, and plan the campaign to that number rather than to the opportunity.
Prepare for the drop
The period after the peak is quiet, and buyers who scaled into a seasonal high often carry the same budgets into a market that no longer supports them.
Decide in advance when you will scale back down. It is much easier to write that plan in September than to accept it in January.
Previous in this series: the ad tech terms people use incorrectly.