countering jab w/ cross

[shs101]

as a southpaw Ive noticed a good counter to their jab is to intercept it with a cross. Im looking to start adding this to my game and change it up instead of parrying to jabs.

Looking ot mix things up just wanted to get any advice on this or ways to pull this off better.
Also how can I guarantee a jab and not get caught with a hook?
thanks in advance