When Does a Toddler's "No" Mean "No"?

There are a few ways to handle these situations:
Give 2 choices. Do you want soup or sandwich for lunch? That way no, is a harder answer to give.
Do not ask. Instead of "Will you go wash your hands?" say "Please wash your hands." Often we ask kids to do things and are surprised when they say "No".
Ask him what he DOES want. "Do you want to go to the pool?" "No" "Do you want to read a book?" "No" "Ok, let me know when you are ready tell me what you DO want." This works with books, food, clothes and such.
Go with it. Respect his no. Let him know that when he says "No" that you will respect his words and he needs to think about what he is saying "No" to. If he says no to ice cream, then it is no to ice cream. The first time or so, you do this you may want (If he gets really upset) to ask him if he has changed his mind and would like ice cream? Have him ask kindly for it. This is not about torturing your kids, it is about teaching them that words have meaning.
After asking your son a question, tell him to take a moment and think before he answers so that he can give the response that he really means.

Pick the ones that work best for you and your family.

B. Davis

http://www.ChildAndFamilyCoaching.com
Because nothing is more important than family

no is a fun word!
you have received excellent advice so far. don't ask yes or no questions, take the silly 'noes' calmly and praise him when he gives a more nuanced answer.
it's probably not a great idea to giggle at him overtly, it'll just make the 'no' game more fun. but really, this is a fun silly stage. enjoy it!
:) khairete
S.

My son was doing this (just turned 2) to literally every question, until he learned to say "OK" when he meant yes. He still doesn't say "yes".
I just went with my gut. If it was something that I was pretty sure he wanted or liked, I would give it to him, and afterwards, ask him the same question and answer "yes" for him. I think it helped him to put the two together.

A lot of the time he would answer "no" and actually do what I asked him to, so I think the trouble in our case was knowing how to answer the other way.

I agree with Melissa. Maybe he needs to add some new words to his vocabulary.. Also give him choices so he cannot just respond in yes or no answers.

Do you want this toy? "Maybe"?

Do you want to play in the pool or in the sprinkler? "You cannot decide?
"How about both?"

Are you tired? "Do you need a few minutes to decide?"

He just hasn't figured out the nuances of his feeling and the language..
The more you use them yourself, the more he will catch on..

It will feel like you are in a play speaking this way, but this is how toddlers learn to speak with the correct responses..