Tips for making a selection
(This relates to using PSP or Photoshop on a PC)
Being able to accurately select the exact area you want is critical to digital collage.
Here are a few simple tips that might help. Maybe they're obvious, but maybe not. I didn't know the first one for at least a year (being self-taught) and it's pretty important:
It's very difficult, if not impossible, to make an exact selection perfectly in one go even using a graphics tablet & stylus, let alone a mouse. To overcome this, you can make your selection in stages. You can add-to or subtract-from an active selection using any selection tool by holding down "Shift" for add-to and "Ctrl" for subtract-from. This means you can use multiple selection tools in succession to select the area you want (such as lassoo and magic wand).
Secondly, ALWAYS do your manipulation in full colour (not 256 colors or less). Many functions will only work properly in full colour, and some won't work at all without full colour. You can drop it back to less colours if needed when you finish the fiddling.
Thirdly, zooming in really helps. The bigger the pixels, the easier it is to see exactly where to make the selection and which tool would be best to use (eg, lassoo to manually draw around the required area; magic wand to select based on colour tones or lightness/darkness).
Fourthly, feather the selection before you do anything to it. This will soften/average the edges of your selection, making whatever you do to it blend in more subtly with the area around it. The amount of feathering you need depends on things like the resolution you're working at, but 3-5 pixels is a good place to start.
Fifthly, once you've made the selection you're happy with, promote it to a new layer (if you're working in a format that supports layers, that is). That way, you always have the original underneath in case you stuff up whatever it is you're doing to the new selection.
Sixth, do whatever you're doing to the selection/new layer in small degrees. Say you're trying to make a skin tone from the head of one figure match the hands you've taken from another. With the head on it's own layer, you could experiment with the RGB (red green blue) colour balance to try to make it look the same hue as the hands. I always do that sort of thing in the smallest possible increment (say 1% +/- at a time).
Seventh, UNDO is your best friend. If you do something wrong and it looks horrible, as long as you have enough "undo" space set, you can go back to a time before it turned to poo. If only Life had an undo function
Hope some of that makes sense to others - or may even be helpful....