Individual form controls receive styling, but without any required base class on the <form> or large changes in markup. All textual elements with .form-control receive width: 100%. Wrap label and control in .form-group to add spacing.
<form role="form">
<fieldset>
<legend>Legend</legend>
<div class="form-group">
<label for="exampleControl1">Label name</label>
<input type="text" placeholder="Type something…" class="form-control" id="exampleControl1">
<p class="help-block">Example block-level help text here.</p>
</div><!-- /form-group -->
<label class="checkbox">
<input type="checkbox"> Check me out
</label>
<button type="submit" class="btn btn-default">Submit</button>
</fieldset>
</form>