While viewing your file with proofing on, perform any aesthetic adjustments you may need to get the look you want. When finished, flatten the file by choosing 'Layer › Flatten Image' from the menu.
It is a good idea to apply unsharp mask to your image so it retains detail when printed. To do this choose 'Filter › Sharpen › Unsharp Mask' from the menu. A setting of 500% @ 0.2 - 0.8 radius usually gives clean, sharp results but always use to your individual tastes.
(3a)
In order to trim your photo properly, you may require a trim mark around the image. To do this, choose 'Select > All' then choose 'Edit > Stroke' from the menu. Set the stroke width to 2 px, the stroke color to black, and the location to 'inside' as shown below in example (3b).