Being in the big sales on DriveThruRPG is a good thing. Although you may be giving away 25% or more of your profits, the increase in sales more than makes up for it, in my experience.
What I did was make a note of each sale that went by without me, and then tried to write something that fitted into that sale. Then as time rolled on and the sales came around again, I did get featured. It is rare now for me not to have at least a handful of titles in each sale.
There are four things you should look out for.
The first is the most obvious. You need to enable inclusion in the sales. You have to do this twice, as there are two different settings. The first is on your Account page, then Promotion Tools, then Opt- In/Out of Site-Wide Sales. You need to enable your titles to appear in the sale and decide if you want to exclude new titles from the sales. The default is that anything newer than 30 days is excluded.
You now have to do the same thing on your Publisher Hub. In the Promotion section, you need Opt-in or out of site-wide sales. The settings are the same, but you need to set them separately for publisher titles and CCP titles.
The next is to set up your titles correctly using the category or tagging system. Tagging things incorrectly may get you in a sale, but you are unlikely to sell anything. But, not tagging your products correctly can exclude you. You can edit a product, and check what you have ticked or not.
Next is your product description. The filters that DTRPG use read the product page and the categories. So you can explicitly mention Halloween in the product description, even for a product that is not horror but just has a Halloween theme. Try using a few variations such as Halloween, Hallowe’en, and All Hallows or Fey, Feyborn, and Feywild. You have to try and second guess what the tech at DTRPG will use to filter by and that is a black box to us.
Finally, several Community Content operators do not include community content in sales or only some community content. You should lobby the people running the CCP to get them to include CC in the site-wide sales. They should also include a wider range of product tags and categories as well. For example, you cannot tag a Miskatonic Repository title as an Adventure, but cause they have excluded the product type filters. If there was an Adventure sale, no Miskatonic Repository titles would be included! But, maybe Chaosium only wants to sell their official adventures?