How do I consistently shove and tackle people in Assassin's Creed on the PC?
Solution 1:
To Tackle someone you need to:
Be in high profile mode, by holding the right mouse button.
Be running, with your legs, by holding Space or the 4th mouse button (5-button config).
Tackle them with your free arm, by tapping Shift or the 5th mouse button (5-button config).
To Shove people you need to:
Be in high profile mode and running with your legs.
Be ready to shove with your free arm, by holding Shift or the 5th mouse button (5-button config).
Run in to them. As long as you're holding your free arm ready they will be shoved aside.
I also found it a little bit awkward to reliably tackle the correct target, but in general you should be close to and running towards the target when you tap the free arm button, and ideally not when near other people that might be targeted by mistake.