Start by creating a new document that is 13" x 19". If you plan on printing it on the Canon S9000, set the resolution at 180. If you plan on printing it on the HP 4600 Laser Writer, set the resolution at 72. If you plan to print this collage on the HP 4600, make your new document 8.5" x 11". This is the largest you can print.
Open the picture you want to place on the background of the collage. This might be a picture that has a nice subject that you want to highlight. Remember, this picture will have the opacity dropped down to about 40%. Once open, use the Crop Tool and make a 13" x 19" crop of the original. Make sure you match the resolution you set when you created the new document. You can see the picture I choose in Step Three.
Select the picture by pressing "Apple A" and then copy the picture by pressing "Apple C". Go back to the new document you made and press "Apple V" to paste the new picture onto it's own layer. Notice the opacity on the new layer is set to 40%.
Now you need to choose what pictures you want to place on the collage. I choose 4 pictures to place on the collage and using the crop tool I made them all into 4" x 6" prints. I then selected them, copied them and then went back to my collage and pasted them on the new document. I had to then drag them around and make them fit well on the collage.
After I had them all placed were I wanted them, I went to my layer styles and I added a drop shadow and a black stroke to each 4" x 6" print. The boxes below show the settings I choose for each picture.
Now that one 4" x 6" picture has the right layer styles applied to it, all I have to is drag and drop the effects to add them to the remaining three 4" x 6" prints.
The last thing I did was add some text to the collage to help explain the theme I choose. You can add a drop shadow to the text and some other layer style to help it stand out. That choice is yours.