Déjà vu literally means "already seen", but the true sense of the phrase has to do with coming across something that looks or feels familiar, but you can't exactly recall when or where you've seen it or felt it. A person experiencing déjà vu is tantalized with hints of remembrance that hovers just out of the reach of conscious thought. It's an interesting phenomenon, and one that writers can take full advantage of. When readers read your story and encounter a situation, setting, character or conflict that implies a connection with their own experience, they are not experiencing déjà vu (because they can remember their prior experience) but they are engaging with your story, which is something all writers should strive for. Whether readers have connected with your story yet or not, you can exploit the promise of déjà vu in several ways to help them along that road.
The first and simplest way is with repetition. Classic humor theory says that jokes work because of the pattern of repetition. A common method for jokes is to repeat a similar story twice and then tell the punchline when repeating the story for the third time. For example:
Three guys are stuck on a deserted island, when one of them finds a lamp on the beach. He picks it up and gives it a little rub and a genie pops out. The genie looks at the three guys and says: "I normally give three wishes, but since there are three of you, I will grant each of you one wish." Well, the first guy is sick and tired of being on the island, so he wishes to go back home. POOF!!! He disappears. The second one said he, too, is tired of the island, and wishes to go home. POOF!!! He too disappears. The genie then turns to the last guy and asks him what his wish is. "Gee," he says," I'm awfully lonely here by myself. I wish my friends were still here!"
Even if you don't have comedy or jokes in your stories, pay attention to how the punchline got set up here. By the time the genie turns to the third guy, we are eager to find out what he'll say. Repetition, threaded through your story can make your readers anticipate the punchline even if it isn't a joke.
Second, you can get a lot of mileage out of symbols or leitmotivs, objects or ideas that thread through your story and resonate with your readers. The classic example is a ring or piece of jewelry that a nervous character turns around and around. Every time he turns it, we know he's anxious without the author telling us he is. Leitmotivs are themes that repeat, such as a character who loves chocolate, hates dogs, or collects glass unicorns. Whatever unique symbol or theme is connected to the character can be used and exploited to keep readers engaged with the story and feeling as if they know the character like a best friend.
Third, theme. The overall theme for your story should come through in strong, nearly explicit ways. If your story is about "love conquers all" or "suffering is punishment for wrongdoing" or "cheaters never prosper" make sure there are a lot of scenes that resonate that theme and point it out to the reader.
Fourth, subplots. Subplots work like déjà vu in your story. They bring out themes and remind readers of the different interpretations of events and ideas. They feel coincidental to the characters and the readers, but they are very purposeful and take some work and craft to put into place properly. One easy way you can connect with the technique of subplots is to notice things happening in your own life. For example, suppose you are in the market for a new car. As you start looking at cars, say you walk around one or two dealers' lots on Sunday afternoon. Then, all week long as you are driving you suddenly realize the models you looked at are popping up everywhere. Why? You never noticed them before, did you? No. You're noticing them because your recent awareness of them has been raised. You had a visit last weekend from your very pregnant first cousin. For the next 2-3 weeks you notice pregnant women everywhere and wonder when their babies will be due. Use this technique to your advantage in your story. Once you introduce a subplot, refer to it again and again in subtle ways until the main plot is riddled with references to things in the subplot. That's a cheap and easy way to ensure that the two (or more) subplots feel "woven" into the main story.
Like Yogi Berra said, "It's deja vu all over again."