irelia help

i need help with irelia. When i q in to attack and try to e, i miss it on a minion. How do u ensure her e will always hit the champ instead of a minion and how do you trade with irelai in lane. I need to know the combos she uses and to guarantee her e always hit the desired target. like when im against illoai in lane, theres so much shit i dont even know what my e hits.