My daughter is alomost 17 months old and is very aggressive with other children and sometimes adults. I've read the whys on this but I'm still struggling with how to make it stop. She bites, hits, scratches, growls, even when there was no instigation. We've been saying no firmly and removing her from the situation or giving time outs but she does this so often that there is no other interaction because as soon as she is put back she hits again. Any suggestions?
Having read up on the topic, you already know that aggressiveness in a 17-month-old is common and not abnormal. And, you are taking the right approach in removing her from the situation to break the aggressive interaction. Consistency in this approach is also essential. The behavior should never be tolerated, indulged or even paid excessive attention to, and, of course, never physically punished (which just teaches more aggression).
One more strategy to add on to what you are already doing is to begin to model a different response for your daughter. Right now, frustration, lack of verbal skills, impulsiveness and self-centeredness (all normal toddler phases) are working to continue her aggression, but these can be outgrown with time and maturity. What she needs to learn is another way to get what she wants, which you can start modelling for her. If, for example, the conflict is over a cookie, the cookie can be broken in half and a part saved for her after she is done with time-out. If it is over a toy, you can show her how another one can be a substitute. You probably won't see immediate changes in her, but, at least you are laying down the foundation for better behaviors in the near future.