Communications theorist Paul Watzlawick used this situation, where "both American soldiers and British girls accused one another of being sexually brash", as an example of differences in "punctuation" in interpersonal communications.He wrote that courtship in both cultures used approximately 30 steps from "first eye contact to the ultimate consummation", but that the sequence of the steps was different.
This may be accomplished by communicating a sense of playfulness or irony.
Double entendres, with one meaning more formally appropriate and another more suggestive, may be used.
Body language can include flicking the hair, eye contact, brief touching, open stances, proximity, etc.
Verbal communication of interest can include alterations in vocal tone, such as pace, volume, and intonation.
While old-fashioned, this expression is still used in French, often mockingly, but the English gallicism to flirt has made its way and has now become an anglicism.