The first method is to list all of the key dates and events through the year specific to your industry that are worth creating content for. You could begin adding these to a calendar to map out what happens on what date so you can plan ahead.
Come up with another list of brainstorming ideas around any products or services that you could push at different times of the year to match trends in seasonality. When you’re finished, it’s worth seeing if you can tie together any key dates and events with trends in seasonality to create a base of content.
Choose a key topic or type of content to use as a central theme. You can then use that theme to create ideas around, and then sub ideas around the individual ones as well.
Try and think up as many ideas as possible, you can always come back later to refine specific ones and get rid of any that don’t meet your needs. In the end, you’ll have a result that’s easy to see visually, as opposed to creating just a static list.
Another idea to consider could be to use your most valuable business asset to your advantage: your customers. All you need to do is keep a record of the problems/questions they’ve had previously regarding your products and services and work off those. Try putting yourself in the customers’ shoes and look at possible issues from their perspective.
So put on your thinking caps and get brainstorming!