HOW TO GRAPPLE LIKE A PRO

Pulling on the grapple will create tension in the wire and this will help you gain speed and momentum. Using 2 grapples at once and pulling will be even more effective OR PUMP the rope for even more tension OR swing alternating arms.
To maintain speed you will need to swing around the map NOT across it then side to side. Grapple and pull for tension around the map but grapple a platform that is to the side of you (the direction of your rotation) to allow your momentum to swing you around at high speeds.
Grappling at high speeds will cause damage if you collide with enemies so move fast to not only avoid enemy fire but to take them out.
Swinging yourself up into the air is fun and can be useful to hit weak-spots BUT going high like Icarus and falling slowly can leave you wide open to an attack do this maneuver cautiously.
The Zip line is a highly effective tool to allow you to change direction during high risk moments to get out of the way, to prevent yourself from falling and getting GAME OVER, it is also very helpful to help you maintain speed when you are about to slow down, ZIP an enemy to cause serious damage.