To check your image before you print, select an appropriate area of your picture by using the rectangular marquee (remembering to merge/flatten your layers first). Or use the alternative method below.

Alternative: It may be convenient to merge to a new layer whilst keeping the other layers available. To do this go to Layer > Merge Visible AND hold down the Alt key - this creates a new layer merged from all those visible. Use this new layer for the test print. Delete the layer once it's done its job if you wish. In the History palette, the new layer is named 'Stamp Visible'.

Alternatively, copy the image by the File > Save a Copy route if you wish and experiment with changes here - flattening/merging/adjusting, etc.

Copy the rectangular area you selected and paste it to a new layer. Remember to 'switch off' the layer displaying the whole image - as you don't wish to print this just yet.

Print the small rectangular section as seen.

Should changes be required, make these and print again and again if you need to. Remember to move the image between each print, as you can use the same piece of paper to make successive prints for side-by-side comparisons.

When you are happy, return to the original image and make the changes (if any).