Pre-Selecting Form Elements

Checkboxes:

<input type="checkbox" name="test_box" value="1" checked />
<input type="checkbox" name="test_box" value="2" />

Radio Buttons

<input type="radio" name="test_radio" value="1" checked />
<input type="radio" name="test_radio" value="2" />

Dropdowns (<select>)

<select name="test_select">
   <option value="1" selected>Value 1</option>
   <option value="2">Value 2</option>
</select>