How to be assertive with a naughty 5 yr old!! He takes me for a ride. Shouting or showing aggression is not really my style.

You need to set boundaries with your five year old. I had a star system where my Son gets stars for being good and does not get it when he is bad. For shouting and tantrums and bigger misbehaviours, he gets sent to the naughty corner for a time out and he needs to think through his mistake. This will be a major challenge as there will be resistance. I had to put him back to the corner 5-6 times before he realised he had to stay there the first try. You have to be consistent and not give ip. Once your child gets the fact that you are intent on discipline, he will tow the line.