I enjoyed our last 501 assignment so much, I figured it might be fun to share how I went about doing it. Most of you will have already figured out your own ways of achieving similar results, but here's how I turned my friend's and my heads into landing pads for flying cats.
Step 1: Collect your images
Alas, I am not responsible for catasus (or pegacat, if you prefer), although I wish I could claim ownership over such impressive blending capabilities. In a perfect world, you will actually have the rights to all the photos you're working with. In this case, I did not actually take any of these pictures, and I only had the rights to the photo of myself and my bandmate, Andriana.
Step 2: Recolor
This is important. Even if you're making the most ridiculous composite image imaginable, it will look more believable if everything is at the same temperature, vibrance, and saturation levels. Also, I think it's better to adjust each image individually rather than adjust the flattened composite--you have more control this way. Here are some before and after shots.
Step 3: Resize
An easy way to do this is keep a preview window open of you background image while you experiment in photoshop with different sizes for the images you're going to layer on top.
Step 4: Select
Although the quick selection tool is great, you have much more control with the lasso tool. It does require a steady hand, though, so make sure you have enough elbow room to move around wherever you need to! It's definitely a more painstaking process, but it does yield better results.
Step 5: Place
The combination of resizing objects and placing them in the right way can add depth to the composite. In this case, I made the flying kitten really small and put him in the upper right-hand corner so he looked like he was soaring in from farther away.
Step 6: Text
When you know you'll be adding text to an image, it's always a good idea to find a space to put it that's mostly one hue. Use the eyedropper tool and find a color elsewhere in the image that's complimentary to the background. In this case, I used the yellowish hue from Andriana's face because I knew it would stand out against the bright blue sky. If possible and apprpriate, write an amusing caption.
Step 7: Crack up in the lab at the results of your handiwork
Step 8: Send it to everyone you know in an e-mail OR
Step 9: Make it your facebook avatar