Mexican food: How to make skirt steak NOT soggy?

My boyfriend is Mexican-American and he wants me to cook skirt steak for tacos etc. Im vegetarian so I dont know but he says when he makes it that it is soggy unlike when mexicans or his mom makes it. His mom wont teach me because she does not aprove of her son with a white girl. PLEASE HELP. being a vegetarian is like being blind in this matter!