Use of the omni-directional mobility gear allows to fly freely around the battlefield. Maneuvering with ODM is essential to taking down Titans. To defeat a Titan, their weak point - the nape is the target, behind the neck. Severing limbs such as arms or legs will make it easier to attack the nape.
Attacking a limb will eventually sever it.
Locking Titans down and restricting their movements is the key to defeating them.
The use of omni-directional mobility gear consumes gas. Your blade will also become worn and damaged through continued use. You'll need to keep an eye on the condition of your gear and refuel or replace as required.
If you meet up with allies during a battle, you can fight alongside them. You can even give your allies commands, such as "Attack" or "Scatter."
Launch an "Assault Signal" and you'll be able to fight for a brief period of time alongside a troop of allies that come to support you. There are also other advantages while an Assault Signal is active, such as increased attack power and your weapon not becoming damaged.
Playing as Eren in his Titan form allows you to experience a completely different type of battle from that as a normal soldier. Everything you would expect from controlling a Titan will be available, including smashing through buildings and attacks that send other Titans flying.