Over several weeks or months, identify which topics you want to play and when. Think about seasonality and when the demand for which content is particularly high. This is very much based on the products or services you offer.
Gradually develop an annual plan that you talk through, revise and tweak with your marketing each year.
How often is regular? There's no blanket answer to this. While some B2B companies post daily, for others, once a week is enough.
The important thing here is: only post if you have something to tell. Posts that offer no added value to the user are ignored or are even counterproductive over time, as they disturb the reader.