3D character models in The Sims, other apps/sites
Though I'd share a tip on something I recently started doing: I spent the $40 or so on The Sims 4.0, with the intention of using it to make 3D models of characters. The idea is that it helps me develop a character if I have a decent idea of what they look like — and it helps me communicate my ideas to collaborators. (As one of my artist collaborators put it when he saw some of the characters I've generated with it, "It's way better than just sending me a picture of Ryan Reynolds and saying 'looks like of like him.'")
As an example, here's some early versions of the cast of my project "Dispossessed" that I worked up this weekend.
Creating these models helped me figure out some stuff about the characters. For instance, I hadn't realized that the jinn (the blue-skinned guy) manifests wearing the same clothes as whoever's looking at him, only color-shifted. Or that Remy the homeless angel (the third character) has a David Bowie/Tilda Swinton androgynous, alien look to them, or that they have a really slight, willowy build. Or that one of the villains is named Ezekiel Barron (name chosen with the help of The Sims' random name generator), and that he's got kind of a grandfatherly, college professor vibe, despite being evil.
The clothing/hair/etc options in The Sims are a bit limited to begin with — but you can download all kinds of free user-created content and add it to your cast. (These characters are all using un-modded clothes/body/etc options right now.)
(The Sims Character Builder is available as a free download for PC; I bought the full version because I've got a Mac, even though I only use it for the Character Builder.)
There's other 3D modeling options besides The Sims, too. One I've played around with a lot is a website called Meez. Meez is intended as a social network, but I just use it for rough 3D modeling. The Sims allows for much more control over body, etc. But the benefit of Meez is that the clothing options are all free to try on, so you can dress your character up and take screenshots without having to pay any money (unlike with the non-user created additional clothing options in The Sims). Here's a character I created in Meez for one of my projects:
I should note that I'm only using these 3D models as rough ideas of what I'm thinking of — basically the same way I would ref photos I'd send to an artist. I'm not producing 3D models and then expecting the artist to adhere closely to them — they're just rough ideas.