I agree with the giving options option, espeically with clothing. When DS says No to something, I try to view it as him letting me know he needs more control over his life at that minute and remember that he doesn't get a whole lot of say in the grand scheme of things (compared to me!). Or that he's telling me he geniunely doesn't want to do something and I try to remember how many things I do that I don't like in any given day LOL. I try to look ahead and give him warning about when things will change. Giving him a few minutes to get used to the idea and limited options usually works. So if we're trying to get out the door, I tell him two or three things that need to be done first (toys away, shoes on, teeth brushed) and give him the option of which one he does first. Giving a 5-3-1 warning has been helpful - "In five minutes we're going to pack away the toys" then "In three minutes...." etc. This gives him warning and so he can finish up whatever he was playing with. Also, if he looks like he is in the middle of something important, like building with blocks or racing some cars, I will compromise and ask him if he wants to leave X out for later/tomorrow and just pack up the rest of the toys. I think me recognising that his play or activity is important to him goes a long way in gaining cooperation. Play is his work. Sometimes simply waiting and being firm/consistent works too - I let him say no and walk away but I remain at the task (very slowly putting toys away, holding a loaded toothbrush in the bathroom) and give gentle reminders of what needs to happen. A lot of the time he will return of his own accord to help or get his teeth brushed or whatever.

He still says No a lot and we still get tantrums but I try to remember that he is only 2 and perhaps I am expecting too much at too young an age. I try to remember that every situation is a learning opportunity for him and that even if he didn't pack up his toys tonight, he at least watched me do it and he will help out more consistently as he gets older. I may be deluding myself here but it's what I've found helpful with DS anyway. HTH.