It's best to avoid changing the original files to make future upgrades easy.

Customize smarty templates, css styles and icons

Please see: Customizing Themes, edit templates and edit css

Customize JavaScript

Add your custom JavaScript to
styles/stylename/custom.js
or
styles/stylename/options/optionname/custom.js

Customize language files

Add your custom language strings to:
lang/\*\*/custom.php
where ** is the language code.

More info: i18n

Customize profiles

Please see http://profiles.tiki.org

Customize the code overall (new features, etc.)

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Share your improvements

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