Perhaps you're a first-year coach, or perhaps you've coached for seven years and you're still trying to figure it out. No worries! You're providing kids with a beautiful opportunity, and you should pat yourself on the back for that.
Coaching is a huge responsibility though, and you're right to research the role. The advice FIRST provides coaches is hit-or-miss, to be honest. For the most part, we grow into our roles through experience.
Having coached and mentored teams that won international awards, I can tell you that it's difficult to strike a balance between fun and productivity. It's difficult to keep kids on task and accountable while at the same time encouraging them to be free and to explore.
The most important advice I can give you is to seek out world-class resources. Be wary of free online tutorials, guides or lesson plans - these materials are usually produced by veteran FIRST Lego League teams who may or may not have learned good lessons or habits themselves. When taking advice from veteran teams or coaches, you should always find out whether or not their team was successful (and, more importantly, whether or not the team got along). Take the advice with a grain of salt!
My coaching and judging (I'm a tech judge for state and world competitions) is also informed by the fact that I competed as a student 10+ years ago and won 1st place Robot Performance and 2nd Place Champions (best overall) at the World Festival. So, I guess you could say I've gone 'full circle' and experienced FLL from every possible angle!
I felt a responsibility to give back to the FLL community, so I created an online LEGO Robotics Masterclass specifically for FLL students and coaches: https://robot-academy.com/first-lego-league-the-ultimate-guide/