Keith Burgie sorry but your comment is incorrect in most cases.
When providing support on here we must always assume that someone is developing a plugin or theme to be shared and that requires wp_enqueue_script to be used to avoid conflicts.
If your developing a theme or plugin which is not to be shared, then yes you can use the approach in your example however each time a new plugin is installed a conflict may happen.
timelcooley I also recommend doing a check on $_GET['page'] and only calling wp_enqueu_script when the page is one of your plugin pages. This makes for a lighter WordPress and goes further to avoiding conflicts especially when your just grasping all of this.
For example. My plugins page slugs all contain "csv2post_" and using strstr() I check if $_GET['page'] has csv2post_ within the string which might be "csv2post_page_projects". I load many script files and a lot of jQuery UI in this plugin, when the user open my plugins own admin pages.
This is secondary important to what songdogtech has already said however. That is the part you need to learn and get right first.