Sound right. Just click out into the void to release your selection tool, since it will grab nothing. I use the top view, drag your shape over the area with the items you want, hit enter and it will select everything in that area. If it selected something you don't want, simply just hit the control key and click on that item and it will deselect it and keep everything else selected.
Also, another tip, sometimes I move quite a bit of stuff to a new area and it needs to go to a different height, after I select everything I want, I group them and that way I can move it to where I want, and if you accidentally click on something else, you don't have to worry about trying to select all those same items again, which can be difficult, some of them could be contained within a world brush and you would never know it. That's how sometimes things like lights and small models or brushes get stuck within a larger world brush and people forget about it and then you have a leak.