I have two photos and I want to put one onto the background of another. When I make the selection in the source photo, do I have to save the selection or do I just close the window? If I have to save is it Cut or something else? Or do I leave the window for the source photo (old background) open? Also, do I have to go to Window> Images to enable Cascade or Float in Window or Float in All Windows? If I do, which do I choose? Suggestions for how I can move a photo onto a different background? I know how to use the Move tool and the Transform tool. I don't know how to get to those steps.
It is desirable to have the resolution of the 2 pictures the same value, although that is not always possible.
At this stage, I like to put a blank layer between the background layer and the layer with the object, and fill the blank layer with as contrasting color. This allows you to tidy up the edges of the object with the eraser tool, for example. With the marching ants around the object still in place (indicating that the selection is active), go to Select>refine edge, and in the dialog you wil see sliders to feather, smooth, contract/expand.
TIP: If you need to make the selection active, press CTRL+left click the layer thumbnail of this layer.
The first time I tried this I was practicing and both your method and jon99's worked. Then when I was ready to do the actual intricate selection, I notice that all the layers I had onscreen were affected by the mask selection of the Selection tool. I chose mask becase the selection was large and it was easier for me to invert it.How Is that normal. And some of the objects I had pasted in separate layers came out on the background. One reason for this, I think, is that I didn't notice that I had activated (because it was in blue) one of the different layers I had created. How did I mess this up? How can I not activate a single layer I've created when doing this copy and paste? Do I create a duplicate layer? Do I need to flatten the image first?. How can I start over and not have a single image from a separate layer appear when the first time I tried this the whole, correct selection appeared?
I was typing and did not see 99jon's post. Up to step #5 the methods are identical. Step #5 allows you to refine the selection as indicated so that the transposition does not look fake - adjust edges, feather, etc.
I have difficulty understanding your work-flow. What are you inverting? Why are you using the mask option in the selection tool? When you copy/paste a selection, does it not show up on a separate layer? On the move tool's option bar, top left, uncheck the box to Auto select layer. That may help.
If step #5 is an impediment to your progress, don't utilize it.
Here is a print screen to show a typical layer structure in this type of exercise:
I have the background layer, a cork bulletin board
Layer 1 is a selection of the boats from the picture in the project bin, selection made with lasso tool
Layer 2 is a selection of the tree from the picture in the project bin, made with the Selection brush, mode:selection
Note the checkerboard pattern on layers 1&2, denoting transparency.
I selected the pictures with these colors for visual contrast.
Also note the halo around the tree, as I did not apply step #5 to refine the edge.