1. In Visual Studio, include your SharePoint 2010 source project in the SharePoint 2013 solution.
2. In the code source files for user controls, change the SharePoint version from 14 to 15. <
3. You can either use the new feature that is generated or bring the project items into an existing feature.
4. To bring the items into an existing feature, make a backup of the feature.xml.
5. Enable Feature Designer and add the new items from the project you just included.
6. Add the appropriate sections in the feature.xml for the feature upgrade.
7. Add tags back from the original feature.xml.
8. Add all items to the package.
9. Search for controltemplates and make sure /15/ is in the path.
10. Search for \_layouts and add \15\ to the path.
Consider installing in compability mode.