First off, I have a feeling that anyone who says "I don't think about it, I just make stuff that looks cool" is probably following the same rules as the rest of us; they have just managed to internalize them so they don't have to follow them consciously. So unless you have that same sharp instinct, it isn't the best advice. Better to start with intellectualizing the problem, then later begin to trust your instinct as that process becomes increasingly internalized. It is the same for most art. Thinking about function, looking to real-world examples, watching your tech level are all good advice. But above that, at a higher level of abstraction, is the emotional affect and the semiotics. After all, when a prop shows up in a movie it isn't just there to fill an actor's hand. It is there to carry forward the story. So it makes a difference if the gun is sleek and cool or large and ugly. Same for the settings. Within a single movie you can have a variety of emotional affect; in Alien, for instance, contrast the homeliness of the dining room, with the womb-like (and vaguely threatening in a smothering sort of way) of the computer room. I think original Star Trek gets far too little credit for their attention to semiotics. When a character lifted -- or spoke about -- a "communicator," you understood exactly what was going on. The name, the shape, the way it was held all communicated (!) the purpose of the tech item quickly and efficiently to the audience. Whereas Space 1999 had communicators that looked uncomfortable and seemed more than anything else like interview microphones (Commander Koenig here, reporting for Channel 11..) and the guns had everyone in my shop setting staplers to "stun." I dislike the super-crowded greebly sets we get so often these days, with random buttons all over the place and parts that have to be lifted and turned and re-seated in non-intuitive directions. One is always wondering in the back of their minds how the character actually knows which button to press. None of them even have labels! (As a comparison, apparently most of the actors that played transporter techs had already decided how "their" controls work. There's a story David Gerrold tells of one of the actors telling him, the writer, the right way to beam someone up.) Specific advice? You'll see this mentioned in some books on design. Idea is, for semiotic affect you look at something your audience is familiar with and try to abstract something about it that "sells" the same purpose or emotional effect. If it's long and pointy, it looks dangerous, like a weapon. Long pointy hulls are great for fighters, not so great for bulk cargo liners (there's functionality in that as well!) It's hard to make a convincing gun without a pistol grip. You want something that sucks? (in a good way); ribbed tubing for whatever reason screams "vacuum cleaner" to most people. Oh. And thanks for mentioning Ron Cobb. He actually has several very nice sketches of airlocks in the book "The Making of Alien." Plus his symbol set inspired me to draw up one of my own (which I have yet to use outside of role-playing).