As an officer, you are the leader of your troop/platoon. You will be expected to be "the man", as it were. You are not alone, however.
You should have a second-in-command who will be your mentor and advisor, but in the end, the decisions will always be yours. Behind closed doors, he and you may have some heated arguments, but in the end, your decisions will be final. Having said all this, never EVER forget that your second-in-command has a wealth of experience under his belt. That should never be discounted. Ever. He will sometimes oppose your decisions, but as I said, always in private. Once the door is open and you two exit to face a waiting platoon/troop, then you two will speak with one voice: yours.
Your section commanders (assuming you are infantry), will also have a wealth of experience. They are the senior non-commissioned officers of your platoon. But they are also commanders: they have their sections, and they "make it happen". Don't ever tell them "how" to do things, just tell them "what". A Sr NCO will know exactly "how" to set up a firebase, be left forward, or whatever.
Here's the challenging part. You are the top dog, and if ever your positions is challenged, you must be ruthless in quashing it. If, for example, your second-in-command is not truly professional, he may challenge you "in the open". Take him aside, caution him, and if he persists, fire him. Immediately.
(Now, by no means do I mean fire him if he stops you from doing something that could hurt you, or something really rash and dumb, but even then, a professional will stop the action in a way that would not question your authority.)
Finally, this may sound antiquated, but your authority to command comes from Her Majesty. This only entitles you to command, not to rule or abuse or use as pawns. You serve your subordinates by being wise and thinking. This may sound counter-intuitive, but loyalty must always go UP the chain of command before it goes down, and then after your loyalty to your subordinates, it finally goes to you. Yes, you are top dog, but nobody is so important that they cannot be replaced.
