1) Gain Intel
If you're on the hunt for a specific target, you can Interrogate any enemy to learn a Captain's location in the world. Additionally, there are special, well-connected Uruk (Worms and other Captains) that will grant you more information about a Captain, including his strengths and weaknesses.
This particular option can be used on Captains and Warchiefs. When using the Command option, you'll send the Captain on a Mission. What is this Mission. Well, that's up to you. It could be to kill another Captain. It could be a Betrayal, putting a bodyguard against his Warchief. Or it could have the Uruk leave his current leader and have him attempt to join another Warchief as his bodyguard... once he's proven himself, that is.
Dismissing an Uruk can provide you a strong tactical advantage. For example, if you Brand an Uruk he'll stay in your control, and remain in the general area he's currently defending.
Should you end up branding and dismissing Uruk in an area and find yourself in a fight, you can call them in as your reinforcements. Plus, there's a chance that as Uruk Captains kill each other and die, one of your marked Uruk will make their way up the ranks.
4) Death Threat
By sending a Death Threat, you'll take one Uruk (be it a grunt, Captain, or otherwise) and have him deliver a message to another member of Sauron's army: Talion is coming for you. By doing this, you'll set the hierarchy on high alert. The Uruk you threaten will bring a gang with him everywhere he goes, and he'll also start training and leveling up. Granted, this will make your target more difficult to kill, but it will grant you a chance for an Epic Rune, which can end up being the difference between life and death in a heated battle.
5.) Reward hard work
Should an Uruk slay you, there's a chance that they'll (deservedly) work their way into the role of a Captain. When this happens, you'll have a number of options. You could track him down, and exact your vengeance by slaying him, or you could manufacture your own leader of Sauron's army by dominating him, and making him yours.
Using these tools to rule over Mordor's Uruk hierarchy will put you at the head of a mighty force. But, all journeys begin with a single step. Which domination feature do you plan to use most, to bend Sauron's army to your will?