As children grow and learn to be comfortable in their environment they start to explore more. Although to begin with they will check back to see where mum or dad or their trusted adult is, they gradually extend their range. About this time there is a more defined character forming and they start to express their desires and emotions. Unfortunately some of these emotions are overwhelming and difficult for the child to understand. Lacking a vocabulary they resort to screaming, crying or simply having a full blown tantrum.
You can avoid a great deal of frustration for yourself and your child, if you accept and work with this growing independence. How many choices do you make in a day? How many does your child make?
Children understand "fairness" as a concept, even before they can walk. It must seem terribly unfair that they have so little say in their own lives. Offer your child a choice of things. Only offer two simple things to choose between, things which you can live with no matter what decision your child makes.
It doesn't have to be about big things, it can simply be which shirt or skirt to wear today, whether to brush your teeth or wash your hands first. Offering a choice of two things is less confusing. As your child learns to make these small decisions he/she is learning to take a small level of responsibility for their life. If the child has made several decisions then when you decide something for the child, it seems altogether fairer from the child's perspective.
Practising making small decisions makes taking the bigger step when the time comes, much easier. Your child believes he/she has some control and at the same time learns to live with the consequences of that decision. For example, offered the choice of shoes or boots in the morning, a child that chooses inappropriately learns that in some situations shoes/boots are a better idea. The parents are less likely to be seen as the "bad" guys because the decision was made by the child.
Obviously when using the "choices" approach you need to be ready to follow through. Accept the decision, which is why both choices should be ones you will be happy with. Praise a good decision and don't criticise a poorer one. Your child will quickly learn what works and what doesn't.