Annie mentioned in comments using a prologue to set up themes, and that made me think of how character and story themes are set up in the opening of a story. I happen to be working with someone on a story opening, and so it's on my mind.
This is, btw, a good reason to go back, after you've written a draft, to the opening. Sometimes the chapter 1 you first wrote is exactly right (maybe your subconscious "saw" the whole story, even if your conscious had to work at plotting it) and nothing needs to be changed. More often, the story didn't develop exactly as promised in the opening, or the opening isn't adequate to introduce the wonderful rest-of-story.
But one task of the opening is to set up themes and motifs that will be amplified in the story. This doesn't mean stating a theme outright (how boring and non-fictional), but rather setting it up to be explored through the whole book-- giving the reader a preview, an entree, into this issue.
I'm not going to define theme here (I explore it in some depth on my website, I think-- here's a q/a session on theme). But let's say that theme and motif are the way most writers convey subtextual messages or connections: "more than mere words can say." Theme usually is revealed to the reader by the process of reading the story (which is why it probably shouldn't ever be stated out straight-- it should take the whole book cumulatively to create it), while a motif is a recurrent pattern or image or something that links important scenes, characters, events, emotions, whenever it is reused.
So if you read over your draft and think, "Aha! I realize that I'm developing a theme that happiness is precarious, as Oedipus's chorus says: Count no man happy until he dies!", well, good for you! But then you go back to that opening chapter and realize it's just a generic opening, a family having a fun time at a lake. That opening doesn't really do all that much to set up the theme, other than presenting the family as pretty happy.
The danger isn't just that the opening is generic (a HUGE problem, of course), but that the tone of the opening might not fit the rest of the book. If the opening is really lighthearted, it might not fit a grimmer story. And that sort of disconnect between the opening and the rest of the story is hazardous, as the reader might think there's false advertising going on. But really, you want to show the family as happy before you strip it all away from them, right? I mean, your theme is about how we can't trust happiness, so you do probably have to show them being happy in the "before" picture so that the "after" picture can be even more poignant.
What can you do in revision of the opening to make this happen?
Well, one thing is to make it a teensy bit extreme. I know that sounds oxymoronic (teensy bit and extreme? Can extreme be only a teensy bit?) but that is actually exactly right. It's not just a routinely happy family occasion-- it's almost frenetically happy. The parents keep touching each other because they're still/again so in love. The kids are not annoying as they typically are on such occasions (maybe it's only MY kids who were typically so :), but almost heartbreakingly adorable. There are none of those minor hassles that always happen on such outings-- Dad immediately finds a great parking place, the cooler hasn't dripped melted ice all over the trunk. Everything's going frighteningly well.
That's the key. Can you somehow manage to make this incredible good fortune seem a little too much? Like a gold chain glittering in the sun but stretched, stretched, stretched... and the reader feels anticipation and dread, sure it's going to break? And maybe it never does, but it's still stretched too far, still promising disaster, even if it doesn't occur then?
How-- well, I'd be looking at slightly intense modifiers, maybe a bit too powerful verbs. You have to be careful to do this well, because you don't want the reader to think you're just overwriting. Take the diction up one notch, not ten. The sun is brilliant, not just bright. The children shriek with laughter, they don't just laugh. Dad grips Mom's hand, he doesn't just hold it.
Also see if the setting/situation can up the stakes and also provide the opportunity to start up a couple motifs that can recur later (like when the happiness explodes). Maybe the lake isn't exciting enough to build this subtle sort of tension. How about a theme park? Think of how expensive it is to take a family to Cedar Point (I can tell you-- I'm on Cedar Point's mailing list, believe it or not-- for a family of four, not counting hotel and transportation, count on $300, just for entrance fees and food for a day). So maybe they've had to save up and anticipate it for months. Dad probably has bragged to the kids about the FOURTEEN ROLLER COASTERS and they've worked their little souls into a frenzy of desire. (I swear, Cedar Point ought to hire me as a spokesperson. :) And it's really, really a wonderful day. See, schools in Ohio don't let out for summer until June, so in late May the weather is great AND there are no crowds on schooldays, and that is what our lucky family finds. No lines! All rides up and going! A blue sky and yellow sun!
Whatever your setting, try taking it up a notch for more and more and more joy! Lots of joy! Amazing joy! It's not just a day at the lake, it's the day the kids actually get up on their water skis! They're not just going to the first night of a blockbuster movie, but one of the stars happens to be there and signing autographs! They're not just going to a baseball game-- Dad catches a home run!
(And notice that the motifs just tumble out. Roller coaster (up and down). Sports (victory and defeat). Lake (water). Find one of these and see if you can reuse them later in the book in a different form, like Dad and the kids play catch in the backyard while Mom waits for the results of the biopsy.)
The point here is not to make the characters feel dread that the happiness will end. No, the characters are too busy being happy. It's to make the reader worry, "This is too good to last." Suspense is disaster postponed, but the suspense comes from sensing disaster ahead-- but it's the reader feeling the suspense, not the characters. (I think the doubling effect of reading is fascinating-- the reader simultaneusly identifies with the characters and feels/knows more than the character does.)
So that's just an example of setting up a theme. Ask me in comments maybe about other themes, and I'll suggest ways to set it up in the opening. The opening ISN'T the theme, but starts the process of making the theme.