You know how to select, by drawing circles while holding down "shift" right? De-select is the same except you hold down "alt" instead. You can also reverse selection: Select-inverse. make sure you save selection to new layer after working with lasso, don't want to accidentally lose that and had to repeat. During adjustments, it's also a good idea to work on new layers, so you can revert changes by simply deleting the working layer. Easiest way to do this is (after finishing lassoing) to use Layer-convert to smart object. Then Layer-new adjustment layer. For example, brightness only go to -150 on each layer, repeating that on several layers can reach pitch black.
I also agree with Doug, much easier and straight forward to shoot on a clean background, whether black or white. Digital tools are better for touching up, making it whiter or getting rid of dirt on the background.
Photo editing programs such as Photoshop Elements are particularly nice for touching up an annoying speck of lint on an otherwise good shot. That "spot healing brush" is fantastic for such tweaks.
I took photos for 40 years before they invented Spot Healing Brush. If I had back the time I spent dust spotting prints or griping about telephone lines in my photos, I'd be much younger now. I use to have a guy at the lab who spent his entire day retouching and dust spotting things that one person now could do in ten minutes (and better!). A lot of the other things we did to save hopeless photos then are automated today. I'm glad we did not have Elements then. I might have had to get a real job.
There was a book by this Chinese political photographer/journalist from the 1970s, about how they modified photos without digital tools. The amount of techniques and processes involved made filming the (original) star wars look like total armature work.
Jeeze- my first camera saved to a floppy disk! My parents had a one of cameras with the film rolls. My only experience was in college I got to develop some in a dark room.