Characters we can relate to have fears and damage, but moreover, for me they have to be devoted to something - an ideal, a person, whatever. Even villains become much more sympathetic when we're introduced to whatever it is that they love.Kage Baker, author of the Company novels, agrees: "It isn't the way a person relates to his hovercar that makes him memorable; it's what's going on in his heart." No matter what planet or time you're living in, there will be "certain constants in human existence: struggle against poverty, rebellion against authority, love and desire, loneliness, curiosity. Any reader can relate to those." Make sure your character has loves and hatreds that readers can see themselves in, and the rest will take care of itself. Don't aim for larger-than-life - and overshoot. One pitfall with science fiction characters is that authors sometimes make their characters "bigger than life, or archetypal" to let them compete with the big, brash colorful worlds they live in. A common mistake is veering past archetypal, all the way into "over the top, or maybe somewhat cliche." If you do try for archetypal characters, think of the classics from all genres, like Sherlock Holmes' quirky genius or Captain Ahab's drive.
It's enough to say "He climbed into his hovercar" and your reader will get the idea. You don't need to give a geography lesson: "They were sitting in the courtyard drinking fire-palm wine" or "She trudged back from the well, balancing her water jar" or "They looked out across the desert and saw the yellow mountains of Califia before them" all give brief, intense impressions of a place, without stopping the narrative in its tracks or drawing focus from the main character.Find out who's hurting. If your story involves a new situation or technological breakthrough, figure out who suffers as a result - maybe that should be your main character, says Robinson, quoting from Damon Knight (who was quoting James Blish in turn.)