...teaching grammar

Early Saturday morning I must have been dreaming about teaching grammar to my students. What the heck?? I like to sleep in on Saturdays (when the dog will let me) so why was my brain wrestling with "school stuff?" In my half-awake state I was trying to explain why it's correct to say "I went to the store." and "I should have gone to the store." but NOT "I should have went to the store." (I should have came, He should have ate, they should have saw, he shouldn't have stole) Augh! So many native-English speakers make these mistakes and they are the language models that students are exposed to the most. And, sadly, I hear coworkers (who are educated) make the same errors. (It's like fingernails on the chalkboard to me.) So...how to teach this so my students get it? Ideas are rolling around in my brain and something will come to me. What will my next early morning dilemma be? Double negatives? (I ain't got no clue.)