SPOILERS
during the helicopter flight we see the waterfall from the first movie.
Mr DNA gets a return in the movie.
The guy with the Jurassic Park shirt also has a book of Ian Malcom on his desk.
Not sure but in JW the kids take a car, nr 26 or 29. If its 29 it is the car in which Hammond drives when they arrive at the park.
Dr Wu is the same scientist from the first movie which the hatching raptor. This you should know.
In JW the kids enter the old visitors center. They use a bit of the banner When Dinosaurs Ruled The Earth that falls down at the last T-rex scene of the first movie.
The kids in JW see a painting of a raptor. The same at which Lex saw a shadiw of a real raptor.
John Hammond got a statue in JW.
They use the same storage devices for dna as in the first movie from which Nedry steals.
They keep using goats to lure the T-rex
Dr Wu tells in JW that due to using dna of modern animalels the dinos look differend then they looked like milions of years ago. Is this the reason raptors are featherless?
In the original book the Carnotaurus has camouflage skills.