I find by not saying don't do that without offering an alternative seems to help a little. Eg: Instead of saying don't touch the TV say how about we play with your puzzle instead of the TV...it gives them something else to focus on rather than the 'naughty' behavior.
Lots of praise for the positive behavior.
I pick when I give a choice...I may ask do you want the teddy bear biscuit or the scotch finger, do you want the dress or the pant but things like bedtime it is a statement rather than a question...it is time for bed now instead of do you want to go to bed now.
I think if you are not going to follow through with their answer you don't answer the question...so if you ask them if they are ready to leave the park and they say no but you want to leave anyway it is better to just tell them time to go now.
I have some very frustrating days...my two girls are 11 mths apart and 2 and 3...they are partners in crime!!