I think you may need to post some code.
But, if you are doing something like this:
$query = "select id, firstname from people limit 1";
$result = mysql_query($query, $db_connect);
$firstname = mysql_result($result, 0);
<form name="xxx" method="xxx" action="xxx">
<input type="hidden" name="id" value="<? print($id); ?>">
<input type="text" name="firstname" value="<? print($firstname); ?>">
<input type="submit" value="Update">
</form>
You should be fine.
When you submit the form, just grab the 'firstname' variable like:
$firstname = $_POST["firstname"];
(and the 'id' variable, although this is just an example..)
And update it in the database:
$query = "UPDATE people set firstname=\"" . $firstname . "\" where id=" . $id . "";
-- Jason