Both To Kill a Mockingbird and The Help use suspense as a primary technique, creating a high stakes situation rooted in themes of social consciousness (and racial equality specifically).
In each of its parallel story-lines, To Kill a Mockingbird utilizes situations of suspense and in some ways this strategy helps to communicate the importance of the themes of each plot.
"The two plot lines—the attempt to lure Boo Radley out and the trial of Tom Robinson—reinforce the contrasting dual themes of prejudice, ignorance, hypocrisy, and hate, opposed by courage, kindness, tolerance, calm reason—and humor" (eNotes).
The reader is engaged with the story and so comes to care about the issues at hand, which are thoroughly dramatized in the text.
In dramatizing issues of race and equal protection under the law, To Kill a Mockingbird utilizes a trial as a narrative device. Doing so presents a situation wherein arguments relating to the theme of racial equality, prejudice and justice can be fully articulated in the context of the courtroom. In terms of narrative techniques, this choice is also important as it offers a moment of predictable conclusion when the verdict is announced.
While this technique is not exactly subtle, it does effectively create anticipation (because the moment of the verdict being announced is absolutely predictable). Tension derived from anticipation relies on foreshadowing and/or predictability. The reader knows that the verdict will be announced and it will be either guilty or innocent. These two outcomes are not entirely predictable, which generates a true sense of suspense and anticipation.
The Help is largely driven by suspense in its narrative, though it uses dramatic irony instead of anticipation. The device used most heavily and effectively in The Help is dramatic irony wherein the audience and certain characters are aware of facts that are unavailable to other characters in the narrative.
The book that the maids write with Skeeter's help is known only to them, but the secret could be uncovered at any time by Miss Hilly and her cohort. The potential for exposure constitutes the basic source of energy and suspense in the narrative and helps to enhance the sense that race relations are charged with potentially explosive and highly personal weight.
In addition to the strategies of suspense used in each novel, the two books also both present examples of the use of dialect.