This is a quick post while it's fresh in my head, regarding porting your contributed modules to the Drupal 7 API. This post specifically focusses on database manipulation and provides the like-for-like changes. If anything here is wrong, or could be done better, please let me know!
First up, individual results:
<?php
/*
* Remember this?
*/
$value = db_result(db_query("SELECT some_field FROM {some_table}"));
/*
* Forget it! It now looks like this:
*/
$value = db_query("SELECT some_field FROM {some_table}")->fetchField();
?>