Upgrading one version of Adobe Experience Manager (or CQ) to another version can be just as challenging as starting from scratch. Potentially even harder, depending on whether or not you have switched from Classic UI to Touch UI. There is no ‘one right way’ to approach things, as it will depend on what you have to start with. Vinit Kumar Singh has taken his experience and knowledge and put together some general tips and recommendations about what will need to be done, in order to upgrade your AEM site. This advice is available in his blog titled: CQ / AEM Upgrade Learnings. You might find them helpful.