People generally respect those who respect themselves. If you're not wanting to be walked all over for the rest of your life, you must stand up for yourself. This shows people that you value and respect yourself and will not tolerate disrespect.
If you have respect for yourself, people will respect you...You don't have to be a bad ass or show-off to get respect. It is all up to you to show what kind of a person you are. Your "persona" and the people around you will know the type of person you really are.
Everyone knows if you give respect, you most likely earn it from the person whom you give it to; however if someone disrespects you while you're being respectful to them, it's best for you to ignore them. That tells them you have no time for Neanderthals.
You have to give respect to get respect. But trust me, it doesn't work with everyone. Just be aware not everyone respects other people and let it go at that. I have a housemate who is very disrespectful towards me no matter what I've tried. He's been through stuff that makes him a little "off".