Eliot has a lot of tools in her workbox, but her favorite is direct characterization. When we meet Squire Cass, for example, the narrator doesn't hold back: "The old Squire was an implacable man: he made resolutions in violent anger, but he was not to be moved from them after his anger had subsided—as fiery volcanic matters cool and harden into rock" (1.8.30). We don't need to see him lose his temper (although we do), because Eliot tells us that he's prone to it.
Or when we meet Dolly Winthrop, we learn that "she took her husband's jokes and joviality as patiently as everything else, considering that 'men would be so,' and viewing the stronger sex in the light of animals whom it had pleased Heaven to make naturally troublesome, like bulls and turkey-cocks" (1.10.20). The narrator is being a little nicer here, but we still come away from this knowing exactly what to think about Dolly: she's patient and a little humorless, but definitely a good woman to have on your side.
Although the tone is different—Eliot's description of the Squire is more lofty and philosophical (or pompous and pedantic?) than her humorous, indulgent description of Dolly—the effect is the same. No way are we allowed to decide anything about the characters for ourselves. The narrator tells us exactly what to think, which is kind of a character trait in its own: she's a Type A, Grade A control freak.
We've spent some time talking about Eliot's use of dialect (see "Writing Style"), but let's say it again: Eliot characterizes the Raveloe villagers by the way they talk.
This isn't really individual characterization—she doesn't draw major distinctions between, say, the clerk Mr. Macey and the farrier—but she does occasionally draw attention to the differences between the wealthy parishioners and the poor villagers. Godfrey, for example, talks like the narrator, coming up with sentences like, "'Hurt? […] He'll never be hurt—he's made to hurt other people" (1.8. 22), while the villagers are stuck saying things like Mr. Macey's, "Why, you've never heared me say 'Amen' since you come into these parts, and I recommend you to lose no time, for it'll be poor work when Tookey has it all to himself, for I mayn't be equil to stand i' the desk at all, come another winter'" (1.10.15).
But this isn't consistent—mostly, the rich and the poor sound the same. Location, as any Valley Girl can tell you, matters more than class. The city folk who visit for Squire Cass's New Year's Eve party make private fun of the country talk. Describing the city girls' encounter with Nancy, the narrator points out that Nancy "actually said 'mate' for 'meat,' 'appen' for 'perhaps,' and 'oss' for 'horse,' which, to young ladies living in good Lytherly society, who habitually said 'orse, even in domestic privacy, and only said 'appen on the right occasions, was necessarily shocking" (1.11.9).
Really, the only character with distinctive speech patterns is Silas. At Lantern-Yard, and then later when he talks to Dolly about his childhood, his language is full of Biblical echoes, giving his speech a loftier sound and providing a key to his early faith.
Eliot's narrator insists that "our old-fashioned country life had many different aspects, as all life must have when it is spread over a various surface, and breathed on variously by multitudinous currents, from the winds of heaven to the thoughts of men, which are for ever moving and crossing each other with incalculable results" (1.3.2). In other words, the Raveloe villagers are the way they are because they live in Raveloe. Villagers from other parts of England, including other villagers, would be completely alien.
Silas is proof. He's from a manufacturing town in the north of England (where most manufacturing took place in the 19th century), while the villagers are from the Midlands, the middle of England. He's totally unable to integrate into his new surroundings. The villagers assume that his "mysterious peculiarities" come from "his advent from an unknown region called 'North'ard" (1.1.4), and the narrator doesn't contradict them. Even within the village, specific locations—the Red House, the Warrens, the Rainbow—are associated with particular characters and behaviors.
Looks aren't exactly destiny—Silas Marner's appearance changes as he grows more isolated—but they're certainly revealing. The Squire, for example, is introduced as "a tall, stout man of sixty, with a face in which the knit brow and rather hard glance seemed contradicted by the slack and feeble mouth" (1.9.1), and we don't need to know anything more than his "slack and feeble mouth" (i.e., he's a mouth-breather) to figure out that he's not a cool dude. Similarly, we don't need to know more than that Dunstan is a "thick-set, heavy-looking young man" to know that he's going to be trouble (1.3.4).
Eliot also signals right away when we're in the presence of good characters. Dolly Winthrop, for example, is "a 'comfortable woman'—good-looking, fresh-complexioned" (1.10.19), and we don't really need Eliot to tell us also that she's "in all respects a woman of scrupulous conscience […] a very mild, patient women" to know that she's a model of village womanhood (1.10.19). And Eppie's dimples and "curly auburn hair" (1.16.4) give us a quick insight into her charming and light-hearted nature.
This easy association between appearance and character emphasizes the novel's allegorical aspects. In a fairytale, beautiful people are good, and ugly people are bad. What's going here doesn't seem much more sophisticated—or is it? What about Silas, who isn't exactly pin-up material?