Before you start editing your photograph make sure you duplicate your layer so you can go back to the original if anything goes wrong.
Step 1: Create a poster
To give your photo a poster feel there's a great Photoshop filter
so go to Filter>Artistic>Poster Edges and have a play with the edge thickness, intensity and posterisation sliders. Try not to make the black lines too thick though as the image won't look right.
Step 2: Halftone
To give it that old comic book printing feel duplicate the layer you've just posterised and go to Filter>Pixelate>Colour Halftone. A radius of around five should work fine but if you want to increase the size of the dots that will be applied to the image use a larger number. Hit OK then change the blend mode to Darken and reduce the opacity slightly to lower the intensity of the effect.
Step 3: Create a frame
Comic books aren't comic books without their frames so we are going to extend the canvas size then fill it with white to give us an edge to work with. Go to Image>Canvas size and increase the size of your canvas. We did it with percent but working in cm, inches etc. isn't a problem if that's easier for you. Then create a new layer, rename it fill and go to Edit>Fill. In the Use drop down menu select white then hit OK. If your layer is covering your image simply drag it under all the layers you've created in the layers palette.
Step 4: Outline the frame
To add the black frame these images have when printed into comics create a new layer, rename it frame then select the rectangular marquee tool and draw around the edge of your photo. Once selected go to Edit>Stroke and pick a width of around 5 pixels. Make sure the location is set to centre then hit OK. Your image should now have a black frame around it.
Step 5: Hand drawn
It looks great as it is but to give the impression that it's hand drawn we are going to give the line a little bit of a wobble. To do this go to Filter>Distort>Ripple. Change the amount to around 12%, make sure size is set to medium then press OK to see your straight line turn a little curvy. If you want to increase the effect even more go to Filter>Blur>Blur more to soften the edges of the line.
Step 6: Text boxes
No comic is complete without a few speech bubbles and text boxes. First, lets look at creating a text box in the top left of the image. Select the Rectangle Tool and draw your shape out. A spot of colour works well in these so double-click on the layer to open the Layer Style Window and find the Gradient tab. Yellow to red or orange works well and you can adjust the colours and how/where they blend by clicking on the gradient. Change the angle so it flows from left to right instead of up and down too.
Next, select the stroke tab and set the size to around 3 pixels and make sure the position is set to outside and the colour Black is selected. Click OK and your new text box will be in place. To add the ripple to the stroke on this box make sure the layer is selected and repeat the steps you applied to the frame.
To add text to this box Select the Text Tool, click over the box and type away. There are plenty of Text styles to look through in Photoshop and there are also fonts you can find online specifically designed in a comic book style.
To enhance the comic book feel try increasing the size of the first letter and changing the colour. Do this on a separate layer though as this way you can use Layer Styles to further enhance the letter. Double-click on the layer you have written the first letter in to open the Layer Style box and create a Drop Shadow to lift the letter off the page. Try changing the angle and reduce the opacity slightly to stop it becoming too overpowering. Next, add an inner shadow to change the overall tone of the letter then add a stroke to the outside of it to create the impression someone drew around the outside of it.
Step 7: Speech bubble
To draw a speech bubble create another new layer and rename it speech bubble. Select the Pen Tool and click points where you want lines to appear to form your shape. Holding down shift while you do this will ensure your lines are straight. Once complete right click on the shape, select Make Selection then when the window opens just hit OK to turn your bubble into a row of 'ants'.
As we've done previously we are going to give this shape a frame by going to Edit>Stroke then go to Edit>Fill making sure white is selected. Once this is done go to Select>Deselect and your speech bubble shape is complete.
You can add text the same way we did before with the text box in the top left corner but this time just use all the same coloured text.