While you may eventually be able to do this withhtml5 scoped styles, it's not currently possible in most modern browsers.
You will have to give your plugin elements a class or id, and manually "normalize" those elements within your plugin's css file (or via javascript).
edit:
Expanding on my answer re: @Tibos comment: you can never be absolutely sure your plugin elmenets will not be styled differently, but you can provide a reasonable amount of specificity in your css by namespacing your plugin with an id:
#myPlugin .container {
background: #fff;
}
#myPlugin input {
border:0;
}
There is, as Tibos mentions, the nuclear option of !important
but it may be best to save this for extreme situations (like the layout completely breaking). It's typically a good thing to give your users the chance to overwrite your styles if necessary.