Always brush from the ends up, holding the hair near the bonds with your other hand so you don't pull on them.
Sleep with your hair fully dry in a loose braid, ideally on a silk or satin pillowcase. Friction is what tangles extensions most.
Use a sulfate-free shampoo and keep oils and masks away from the bonds; apply them from mid-lengths to ends.
And don't skip maintenance. Moving the bonds up on time is what keeps them invisible and comfortable.