SELECTIONS
1) Open your image in photoshop. You can use masks, magic wand tool, pen selections etc to make selections, but they can still leave hard edges.Quick Selection tool (in same slot as Magic Wand) can be used similar to the magic wand tool, but by dragging strokes on the image rather than clicking points.
You can duplicate the layer, and adjust teh levels to make selections easier.
Ctrl + H = Hide marquee of selection
The best way to make a complex selection (a persons hair etc.) is to make a quick selection, then use the refine edge function by right clicking on the image and choosing ‘Refine Edge’. Note that CS5 is required to use this feature properly. Then you can paint in any areas the selection initially missed.
COLOUR CORRECTION
1.Put an image behind the cutout. You will notice that the cutout doesnt match the colour info of the background. Open teh levels box from image>adjustments>levels and adjust the input sliders to better match the BG.
2. Now adjust the Hue/Saturation of the image by going to Image> Adjustments>Hue/Saturation. Adjust the hues to match the lighting of the background. in this instance, make the hues a little greener, and up the saturation slightly.
SMART OBJECTS
For resizing objects, and you dont want to lose quality if you scale it several times, convert the layer to a smart object. Right Click the layer in the layer panel, and choose ‘Convert to Smart Object. This saves the layer as a separate file , so each time you resize you just get an instance of that separate files.
Also, if you have several instances of the same smart object on one image (ie lots of stars) and you decide you need to edit these stars, you can edit the base smart object by clicking Layer> Smart Objects> Edit Contents. This will open the smart object as a separate photoshop file.
When done with your smart object, you can right click and choose Rasterize layer to convert it back to a normal layer.
SPOT HEALING TOOL
To remove blemishes from skin choose the Spot Healing Tool (Icon just above the brush tool). You can paint over blemishes and Photoshop will calculate the area around and try to match whats under your brush with whats around it. This isnt precise, so requires care to use. It can be used in landscaping, to eliminate rocks on a hillside, or tire tracks in a field etc.