Creating apparel mock ups are quick and easy when you have the right tools and software know-how. Follow this tutorial to save time and look like a true professional. Step 1: Finding High Quality Stock Imagery Design By Humans has a nice variety of colors and each set includes male/female and front/back images. Just scroll through the available colors and click on the one you want to use to download the folder. Hint: It's best to choose a color that's close to what you're looking for, you can adjust it later.
Step 2: Creating a Displacement Map Maps are great ways to add depth/dimension to an otherwise flat graphic. Using one of your t-shirt images, create a map by going to the channels palette and selecting the channel that has the most contrast. Make a copy of this channel, then control+click and select duplicate. Drop down the document section and select new, then name it tshirt_map. Hit ok and you now have a new file created from the channel you selected. Add a small amount of gaussian blur (1-2 pixels depending on size) then save your tshirt_map as a psd file and close it.
Step 3: Applying the Map to Your Graphic Return to your original t-shirt file and open your graphic to be applied to the shirt onto a new top layer. With this new layer selected go to filter>distort>displace. A new window will appear, but no changes are necessary in these settings, so hit ok. A file menu will pop up next. Select the tshirt_map.psd file you created in the last step and you will notice the distortion affect has been applied to your graphic. This is not quite enough, however. To make a more believable t-shirt you must now experiment with a variety of blending modes and fill percentage to add texture and depth.
If you'd like a more in-depth explanation of this process with visuals check out Josh Johnson's tutorial at designshack.net.