Brainstorming is the key, take each one of your ideas and scrutinize it from all perspectives. Ask the journalists' questions (how, what, why, when, etc.) and read as much as possible. If its a technology or programming language you daily dabble in, the content should come naturally to you.

As for the problem of having the content all in your head but still being unable to put it down on paper (or laptop screen), I can understand and empathize with that problem! Writer's block can be due to many reasons but the best way to solve it is to just have a ritual of just sitting on your desk daily at a stipulated writing time. Even if writing doesn't come to you in the beginning, it will eventually flow as you make this a habit. In many trades, success is just a matter of showing up, its the same about writing.