First of all, we are going to find out what a vanishing point is exactly. In a perspective view, the vanishing point is a point toward which a series of parallel lines seem to converge. Vanishing points can also refer to the point in the distance where the two verges of a road appear to converge.
I have outlined those lines, which lead us to the vanishing point. We only need 2 diagonal Lines for this. The red outlines are hints for looking in the image for drawing perspective guidelines.
Create a new layer and name it "lines". Zoom out by Holding ctrl key and pressing - (minus sign in numeric keypad of keyboard) and draw a diagonal line with the help of the pen tool. Select the pen tool and make sure that the "paths" option is selected in pen top toolbar and not "shape layers". Now click on top right and then click on left bottom as shown in picture. A line path will appear appear.
We have to align it correctly with edge of table. To do this click pen tool for while and a pop-up menu will appear, choose "convert point tool" from it. Now click on the line path, its handle (small square) will appear on both sides of line. Press ctrl key and drag any one of the handle of line path and place it correctly aligning with table edge.
In this step, I have created another path using the pen tool. Make sure it aligns with bottom edges of the cabinet as shown in the picture.
Now we need to stroke these two paths. Make sure the "lines" layer is selected and current tool is "Convert Point Tool". Now right click on any line path and choose command "stroke path", in the stroke path window select "brush" from the drop down menu and press OK. The line path will be stroke (paint) with the current brush setting.
The brush tool can also be used for drawing straight lines. Select brush tool, click from where the line has to start, press and hold Shift key and click where line should end. A straight line will be drawn. If the line is not correctly drawn, press ctrl+z keys to undo and try again.
The yellow point is a vanishing point, which will help us to draw guide lines and then draw boxes or whatever shape we want to use. For simplicity, I am using boxes for drawing.
Create a new layer and name it "Box front". Select "Rectangular Marque tool", hold left mouse button and drag to create rectangle selection as shown in picture. To fill this selection with foreground color, press and hold Alt key and then press "delete" button, selection will be fill with current foreground color.
Now select the "Lines" layer, draw lines with the help of pen tool or brush tool as shown in picture. Make sure that these four lines are starting from 4 corners of the green rectangle and ending in the vanishing point.
Create a new layer and name it "box back", then draw another rectangle of a different color. The 4 corners of this rectangle should be on 4 perspective lines, which are leading to vanishing point. Put this layer beneath "front box" layer.
Create a new layer on top of "Box Front" and "Box back". Choose "Polygonal Lasso tool", and create selection for the upper part of the box and fill it with yellow color.
In this step I have created another box using the same technique of drawing perspective lines and then createda box with four sides without upper part to visually see lines and the depth of box. Notice how guide lines from vanishing point are used for creating this box.
In this example we will put floating objects using vanishing point. The source we are using is http://www.sxc.hu/photo/1064959.
Red circled locations, are hints to be used for drawing two diagonal lines guide, for finding out the vanishing point.
Two line paths created with pen tool.
Create a new layer and name it "lines", now stroke these paths. The lineguides are on its own separate layer, therefore we can hide them.
Draw a shape as shown in the picture using any drawing tool.
Draw a smaller rectangle of the same color with slightly darker shade, for showing the thickness of object.
In this example we have 2 vanishing point. Determining vanishing point for these type of images are tricky. We have to zoom out from canvas, until we see where two lines are crossing each other.
In this image, I have drawn four lines, using perspective guides from the image. We can see that we have 2 vanishing points on both sides of image.
Green guide lines from the left vanishing point will be used to draw or place a frame picture on the wall.
Draw a yellow rectangle frame on the wall using guide lines from the left vanishing point.
To make it simple, I have drawn boxes and shapes for placing in a image, but if we want to place a real object picture, we need to find sources which look identical as drawn in previous steps or we need to transform and reshape, using warp tool or free transform tool.
I hope that it will help you to place objects correctly in perspective.
Final Result of drawing two boxes.