In the opening scenes of the film, Kylo Ren's identity is foreshadowed. We know Lor San Tekka, the man who gives Poe the map, is an old acquaintance of Leia, and he knew Ren before his turn as well. Turns out he knew both of them for the same reason: Ren is Ben Solo, Leia and Han's son.
A variation with Chewie's iconic bowcaster — the film goes out of its way to point out its sheer hitting force. Everything it hits is blown back and knocked out in a single shot. Except for Kylo Ren, who is badly wounded by it, but essentially walks it off.
Han says early on that he'll talk his way out of a situation; he does it every time and gets upset when Chewie calls him on that. Han tries to talk down Kylo Ren into a HeelFace Turn, but Kylo refuses and kills Han.
Bala-Tik's first words to Han Solo; "Han Solo! You're a dead man!". By the end of the movie, Han is, thanks to his own son.
Snoke outright tells Kylo Ren that facing his father will be his greatest test. As noted, with some effort, he passes. Or fails, if one takes the novelization at its word that the exercise weakened Ren's resolve.
Upon entering Starkiller Base, Han grimly remarks that the longer they stay there, the more quickly their luck will run out. After finding Rey, they choose to stay and help Poe's squadron by blowing a breach into the base's weak point so it can be attacked in full. This decision leads to Han's death, Finn nearly dying after a lightsaber slashes his back, and Rey locked in a lightsaber duel with an increasingly unstable Kylo Ren. Talk about luck running out.
Ren sees an image of an island in an ocean in Rey's thoughts. At first it seems like a callback to Rey dreaming of a better place than Jakku, but it foreshadows where Luke is hiding.
In her vision, Rey hears the voice of Obi-Wan Kenobi, foreshadowing the reveal of Kylo Ren's true name, "Ben", which was Obi-Wan's alias while living on Tatooine.
When describing the Force to Rey, Maz Kanata tells her to "Close her eyes. Feel it". Later during the climactic final battle on Starkiller Base Kylo Ren chases Rey to the edge of a cliff, the world falling apart all around them. He offers to teach her the ways of the Force, giving Rey the incentive to tap into it. She closes her eyes and feels it before overcoming Kylo in combat.
In the opening of the film's second act, Finn tries to help Rey fix a leak on the Millennium Falcon, but is more a hindrance as he cannot tell the tools apart. It's a subtle sign that he has limited-to-no-knowledge regarding engineering; he knows what Starkiller Base can do, but he has no knowledge on how to shut the shields down on his own as he did not help build it.
Han tells Finn and Rey about the Force, saying "The Dark Side, the Light?... the crazy thing is it's true." You think he's just recounting the events of the original trilogy, but eventually, we find out his son Ben was seduced by the Dark Side of the Force and became Kylo Ren.
Finn's brief fight with the stun-baton-wielding Stormtrooper establishes that all First Order troops have some melee training, explaining why he lasts as long as he does against Kylo Ren.
Rey being Force sensitive is hinted twice before she touched Anakin's old lightsaber:
Rey has limited piloting skills but is capable of piloting a "garbage ship" that hasn't flown in years (aka the Millennium Falcon) through tight and narrow spaces, not to mention that she does this without the help of a co-pilot. This somewhat serves as a Call-Back to The Phantom Menace, where Qui-Gon mentioned that Anakin's ability to pilot a Pod Racer is because of his latent Force powers.
After a Rathtar caught Finn, Rey is able to severe its tentacle by timely closing a door. She later simply said that it was just luck,