Autodesk Inventor has a number of powerful selection filters that enable users to quickly and easily select the geomtery they want to work with.
Selection filters are available in all the different 'modes' within Inventor e.g. part design, assembly design and drawing layouts and can be accessed via the Quick Access Toolbar:
Or my favourite way of accessing the Selection Filters list is to hold the shift key on the keyboard and then right mouse click. In the part environment you would get this menu where you can choose to filter your selections on features, faces, edges, bodies, groups etc:
In the assembly environment you would get this menu:
You then have quick access to all the different types of filters to help you select exactly what you want.
As an extra tip, if I want to edit a feature of a part whilst in the assembly, I just right mouse click and choose Select Features and then without having to activate the part, just highlight the feature, right mouse click and select Edit Feature.
This saves me having to selecting editing the part as it allows me to edit a feature at the assembly level.