What are the signs and behaviors that show that a girl is loose?
I'm hoping you are asking this to know which girls to avoid.
The Bible list out numerous warning signs of immoral women:
Immoral girls learn to use flattery, sweet words and smooth talk to get their way (Proverbs 5:3; 6:24; 7:14-21). Like a salesman, she gets a boy focused on what is being said so as to not pay attention to what is being done or being encouraged. An immoral girl flatters boys to stroke their egos (Proverbs 2:16). By getting a boy to think he is something desirable, he doesn't stop to question why a girl is interested in him.
Immoral girls often have a bad home life, so they rarely spend time with their family (Proverbs 7:11). Instead they wander looking for excitement and attention (Proverbs 7:12). They really don't know how to have a stable relationship, so they rare stay with one boy for long (Proverbs 2:17; 5:6). She really isn't interest in boys as companions, she sees them more as a means to an end (Proverbs 6:26).
Immoral girls aren't interested in religion or following after God (Proverbs 2:17; 5:6). These things are seen as boring or interfering with what she desires to do. She talks about doing things that are wrong and breaking rules, knowing that if a boy will break rules in one area, he'll break other rules as well (Proverbs 7:11; 9:17; 23:28). She doesn't see her actions as sinful (Proverbs 30:20).
Immoral girls seek attention because she can pretend that she is wanted if boys are paying attention to her. Thus she will use her body and the way she dresses to capture a guy's attention (Proverbs 6:25; 7:10). She'll talk louder than she needs too and act in an over-the-top fashion to get guys to focus on her (Proverbs 7:11; 9:13). She'll also act in a brazen manner, such as using intimate behaviors with boys she doesn't know or barely knows (Proverbs 7:13). Such girls know that if they get boys turned on, they don't think clearly.
A weak area in most boys is a desire to be the rescuer of the damsel in distress. Whether on purpose or accidently, immoral women play on that desire by acting ignorant (Proverbs 9:13) or being a victim.
Women are no different than men in wanting to have stability in their lives, but immoral girls try to create stability artificially. She figures if a guy is dependent on her or needing her, then there is stability (Ecclesiastes 7:26). This is why sex is used to trap a guy into continuing to come back for more. But she also strives to keep him off balanced, never knowing if he is really going to get it or not because that gives her the illusion of control. She aims to keep the boy on the edge of begging favors from her and in granting them, she feels she controls him and her own life. This is why you find boys involved with such girls frequently complaining about how often they fight and how they never know where they stand with a girl.