Hi,
a look to the bases of HTML give you the solution:
In <input> tag you can use "value" option:
<input name="day" values="<?=date("Y-m-d")?>">
In a <textarea> just echo the value:
<textarea><?=$mytext?></textarea>
In a <select> print SELECTED in the right <option>:
<select name="sel1">
<option value="0" SELECTED>Default select</option>
<option value="1">Other select</option>
</select>
In a <input type=checkbox> echo CHECKED:
<input name="opt1" type=checkbox CHECKED>
...I hope this helps