Working with complex objects is easy in Inkscape due to the cocept of groups and layers (that makes it a far better candidate to do UI mockups than GIMP btw).
Inkscape provides means to select objects overlaid on top of each other with Alt+Click, but also allows you to press Tab to cycle objects in the DOM tree. When you have groups, things get tricky as you need to add Ctrl to the game and you’re on your way to sore fingers.
Thus today’s tip – you can actually ‘enter a group’ by selecting it and pressing Ctrl+Enter (or double clicking). Now it appears as if you just unselected the group, but from now on you can normally select individual objects in the group using the regular methods, until you press Ctrl+Backspace or select an object outside the group.
Update: I mixed up Ctrl and Alt, corrected. Thanks Bulia.