J.J.
One thing i believe helps is to reduce the use of the word No around the house for other things. "do you want pasta dor dinner?" "I think i'd rather have..." instead of the word NO.
Like when you get "i want chips", and responding with "no", instead try to say "i'd rather you had some fruit, oh it's so yummy, mmm.. maybe so yummy that mommy will eat them all, but if you like, i'll share with you!" then he thinks if he doesn't try what i'm raving about, he'll miss out on something good.
And when you get "no" to pick up your toys, or let's get undressed. instead of NO, don't take more toys out, or No don't make more of a mess, or NO we're getting a bath NOW. I say, Ok then, daddy and i are gonna be the GOOD kids and pick up because GOOD kids pick up their toys and get a reward! so we'll start and i'll say "daddy you're so NICE to help pick up, you should get a popsicle for helping..." and my son will JOIN RIGHT IN! so we cheer "YAY - THANKS BUDDY!" the proud smile on his face ROCKS!
With the bath, it's, "Oh if you aren't going to get a bath, then i'll have to have all the fun splashing and playing with the cups and bubbles all alone then.." maybe even hubby will chime in "Ohhh can i have a bath, that sounds fun!" and my son will be headed up the stairs in a heartbeat to start the water in the tub.
It's hard to cease all use of the word no, but we really try to reserve it for the bigs things like, NO HOT! and danger situations.
HONESTLY don't get me wrong, we use the word, just less lately. and we also try to say Uh Uh... or Please don't...instead.
BEST OF LUCK!! and know that it's the AGE... NOT YOU!