Especially with toddlers whose language is still not very developed but whose determination to do "by self" is at its peak, you can often avoid tantrums by giving a choice between two options that are equally acceptable to you. So, if you ask your twin to put on "this shirt" you're in for a struggle, but if you offer him the choice between a red one and a blue one, he'll be happy to exercise his power and independence and make a choice. More than two options can be overwhelming for a two year-old, so stick to two simple possibilities.
Aggression between Twins
Dealing with aggression between twins is often the hardest task for parent. They wonder how much they should intervene in fights, how much to protect the "victim," and worry when one twin is always the aggressor. The first rule in the family must be that it is the parents' job to protect each child from hunt. The second rule is that no one may hunt people or animals. When children feel overwhelmed by aggression, they should be provided with an outlet such as hitting/biting a pillow or punching bag, because "things" do not feel hurt.
Fighting over toys is generally the starting point for aggression. Teaching her means such as "trading" and "taking turns" gradually provides twins with the skills to share in peaceful co-existence.
Older twins may engage in less overt aggression, but tax their parents' patience with endless arguing. Arguing, within reasonable limits, has some important psychological functions. It is part of the process of twin individuation, and it deflects some of the tension that in singleton families would exist between parent and child (as well as siblings). It also gives twins the unusual opportunity of struggling with an equal as opposed to a parent or order sibling who has more power in the family, or a younger sibling who will, naturally, be more protected by the parents. Parents should set limits on arguing such as no physical fights, no obscenities, or no fighting during dinner, but should refrain from forbidding or intervening in every argument.