Alright, so it looks like there's a bit of a demand on finding and using references when it comes to drawing purty pictures. Here's what I've managed to learn. If you have questions, comment or shoot me a note on deviantART.
This tutorial will focus on the concept of finding a photo reference for a drawing of a human, but it will hopefully extend its usefulness into finding references for animals, aliens, or even nonliving things.
1) What makes a good reference?
Obviously in order to find something you need to know what you're looking for. Life is the best reference, but that's not nearly as easy or convenient as using the internet. Photos of the real thing are the next best reference. Someone else's artwork is fine for inspiration, or maybe to try copying that cool lighting effect, but try not to use it as the main reference for your own work.
When you draw based on someone else's work, you pick up their bad habits and mistakenly think their mistakes are correct. A photo, unless heavily manipulated, will always show things truer to life.
In short, use photo references when possible.
2) So where do you find a good photo reference?
This can depend on what sort of reference you need. If you're looking for anatomy references, there are websites dedicated to things like that, and Artists' Hospital actually links several. However, I'm focusing on pose references, so we're gonna venture into stock photos! However, it's not as simple as running to Google and hitting flying angel sorceress. It takes a little more persistence and imagination.
deviantART is not a bad place to look. There are lots of great stock collections out there, and I love Jade Macalla and Senshi Stock, personally. However, if you really want to get into large collections, I suggest looking at royalty-free stock photo websites. While the intention of these sites is to sell high-resolution images for companies to use on their printed goods or websites, the thumbnails of said images often provide great references.
Two of my favorite sites are www.dreamstime.com and www.gettyimages.com. Stock sites have millions of images available, and that's a good thing, since I'm not kidding when I say I often glance through a thousand thumbnails when planning one drawing. Even photo sharing sites like Flickr can be valuable resources, but I tend to have the best luck with stock websites.
3) How do you find exactly what you need out of so many photos?
Separating the good stuff from the junk you don't need. Finding that one picture... the actual work part.
No photo will ever be a perfect match that exact image you have in your head. This is where flexibility and imagination come into play. While it's important that you have a concept in your mind, you also need to be willing to change that concept if you find a great reference that's just a little different. I will often think of a concept, say, a girl lying on a couch looking upside down at the camera. It's specific, but it's also flexible and open to interpretation.
After that, it's time to hit up the stock sites and look for something that I want to use. There are tons of beautiful pictures of young women lying on couches, but with a little effort, I found one with a great angle and great potential.[link]
That picture was great because it let me add the quirks I wanted, which turned out like this[link]
4) What kinds of search ideas are a good place to start?
When it comes to simple poses, like girls on couches, try searching for exactly those. However, when it comes to getting more complex or action-filled poses, you really need to open up a bit more. Sports and dance photos are great places to start. They demand an intensity and grace that few other activities do.
Forget ballet, this girl is just about ready to drop an axe kick on somebody. I feel the way she's shifting her weight in this pose is the best part of the reference. Shift those arms into a battle-ready form and she's good to go.[link]
A secret agent doing a spectacular getaway dive while shooting upside down at his pursuers.[link]
Beach towel? I see a military commander like Roy Mustang looking down over his cape at his subordinates.[link]
Lastly, don't be afraid to make changes to a pose. Couch girl needed to be upside down. Swooping Sorceress needed to be swooping in control and not falling. The entire act of finding these references is scanning for images that you can make your own.
Keep your eyes and your mind open.
5) Tips and misc.
-When using Dreamstime, after you search, make sure you look at some of the search refine options. Check the with people box and uncheck illustrations at the least.
-When using Getty Images, the site has a great set of search refining tools. Explore them.
-When you do a search, always look through every thumbnail, even if there are a couple thousand. You might just get surprised. Set it to the max number of thumbnails per page and it will go quickly. (this does not mean you shouldn't narrow down your results)
-If you're comfortable with it, turn off safe search. There have been times where the picture I needed was blocked by safe search. Just because the model might be wearing lingerie or just might not be wearing anything doesn't mean it's not a good reference.
-I hope after all this you can also understand how it applies to non-human subjects. Want a dragon? Look up reptiles, birds, bats, maybe even horses.