Best way for a interrupt?

I'm starting to try to tank in the game and I need to have more focus to interrupt as a warrior, but I can't figure out which will be best for me as I dont have the reaction speed to interrupt manually before someone else does, macros I find too hard and confusing and weakauaras I find arent working I thought one had a icon on the screen for me to click to interrupt a spellcast as I click it but no luck