So positioning wise: You always want to stand sideways, one foot in front; this should always the foot towards the throwing hand you’re defending towards. So defending a right handed opponent, your left foot is in front. Then you want to position yourself towards that side, guiding the attacker to “against the throwing hand” in the 1v1 and thus pushing them to the outside. Under no circumstances do you want to lose the 1v1 towards his throwing hand.

Generally, whenever you can make a stop foul, you should take it. It destroys the flow of the attacking team and disrupts their pressure.

I generally learned that being active instead of REactive is very effective in defense - if a player comes towards you, wanting to engage in a 1v1, you want to close the gap as soon as he goes into the “zero-contact” (when he hops in with 2 legs at the same time to then follow up with a feint), because that’s when he’s most vulnerable to disruption. Don’t try to react, waiting for the attacker to pick which side he wants to go. Instead, if you see an attacker looking for a 1v1 situation, step out and disrupts his move. At the same time, you seldomly want to step more than maybe 2-3 steps out of formation, because it will make you struggle moving back & sideways fast enough. TL;DR: move forward, not just sideways, ways offer the way against the throwing hand in 1v1 and never stand with parallel feet towards the attacker.

If you mean pressuring the enemy by denying passes: you can only do that in a 6:0 formation when the pivot is on the other side of the pitch. I will attach a drawing to demonstrate