Install then Uninstall then Install then Uninstall...What are you doing?!

Most of those new to Joomla does this: install the component(or module, plugin or template) then you found some error so you'll uninstall it again (to convince yourself that the changes are really taking effect even though you can just edit it) then install again the updated copy. Found another error, uninstall again, then install again.

Isn't that such a hassle? In order for you to not do that install-uninstall-install thing then all you need to do is add this code in your xml installer file:

<extension type="component" version="2.5" method="upgrade">

Yes, that's right! All you have to do is add the method="upgrade" in your xml installer file and you can install your extensions infinite times without uninstalling them first.

Take note that with this it will only override the files that was already installed on the Joomla site. In case you rename one file doesn't mean that the file on installed on Joomla site would also be rename. It's kind of hard to explain so I'll just give and example.

So you have file1.php in your Joomla site. Then in your zip installer file you rename it to file2.php so the file1.php doesn't exist anymore. When you install the extension the file2.php will be copied to your Joomla site but the file1.php does still exist on your Joomla site. Got it?