How to Write a Story That Engages the Reader

I'm writing about stuff that I already know. And I don't need to keep track of as many characters as you do. It's a huge advantage when it comes to starting something new which is the position I'm in right now. The voices in my head start yammering and are engaging me. Odds are good though engage the reader. Talk to us what makes those ideas come together. How do you know which ideas are interacting well together? How do you decide.