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.

It's pretty normal for a emotionally healthy child to take their parents "on a ride". They are testing their boundaries and seeing how far they can go. Thus it is important that you counter this with drawing limits and being firm about the lines you choose to draw with your child. Being firm is often misconstrued as being fierce or aggressive but it is just a form of asserting your views and dominance as a parent. It is important that when you be firm on a matter, to be consistent about it in the future, for example if your child insists on having cookies for breakfast and you say no, make sure you say no all the time and not give in later on in the future.