My mom always told me she liked the age 2 so much more than 3, and I now know why! I have an almost 5 yog and a 2.5 yog, and my 2 yo just started with the nos, too. I had forgotten, kind of, since my older was here! I think it is because kids are so darn smart, they start playing these games. So, I try to get her to realize it is not to her benefit to say "no" all the time.
1. If I say, go get your shoes, and she says "no" (and she does) I sternly say "You don't tell momma no", but I don't swat her or give her time out (they don't work and they are still getting what they want, attention)- unless it is something that might endanger her, because I don't want her knowing the power her saying that has on my sanity! Instead I will say something like, "that is too bad, because we were going to do xyz," and I walk away, completely ignoring her. If her sister is there I then ask her, and since she just heard something fun, she is on it! Then, my little one usually hustles to do what I had wanted and I then say, "oh, maybe you shouldn't say no so fast. Thank you for getting your shoes!" Then I ask her something she will say yes to and tell her that I like that better.
2. My parents laughed at this one, I would literally say "Ready, set, go" after she said no, and she would run to do whatever.(Again, ignoring her "no") Unfortunately, like I said, kids are smart, and that one is starting to not work!
3. If it is really not a time I can wait for her and these little games, I just don't give her a chance to say no to the same thing i.e. "Come here please", inevitable "No", I say "You can come here or I will come get you" and if I have to get her, it is no fun. I take her to where I was and say again, "you don't tell momma no". I may take whatever she is playing with until she is ready to do what I ask. Also, I give her an example of the phrase I want, sometimes even silly, "Yes, momma" or "Momma that is a great idea" or "Of course I would love to do that!" and she repeats it, which can be funny in itself. She will slowly learn (I think and hope) that saying no does no good and is no fun.
I went on and on, but I hope this helps you come up with what will work with your little one. It is all about trying new things until you find what works, and then when they catch on, trying more. Good Luck! This too, shall pass!