Let's get into it shall we?
1. Crossing your legs.
No, it isn't bad for your knees, so don't worry about that myth but what it does do is restrict the blood flow to your legs and knees. What that means is that it will restrict blood going to every necessary vessel, especially under your knee(s). Say hello to spider veins. Sciatica is also something that can present itself when crossing your legs is a constant habit. Your sciatic nerve is the longest nerve in your body (back down to legs) and is painful when pinch or pulled. So if you can't cross your legs how can you sit ladylike in a skirt or dress? Cross your ankles. It's actually prettier than crossing your legs, makes you sit with better posture too!!
This is the correct way (go Dita!!) -->
2. Dragging your feet.
Unless you have a medical problem or are unable to pick up your feet, act like a decent human being and walk properly. It also ruins your shoes, so keep that in mind. When men do it, women will stop looking at you, and when women do it we look extremely immature (men too), so stop. Also, as a result of doing this a lot, you will find that your shoulders will start to hunch, your pelvis will start to push forward, and your all over walk will become strained looking.
3. Chewing with your mouth open.
If I have to explain WHY you should not do this then you have problems. It's called being polite (unless a medical problem prevents you from doing so, as I am not a monster and I understand these things). It's gross and I purposely avoid talking to people who do it.
4. Touching your face and hair.
Do you like greasy/oily hair and having to wash it more frequently? Do you like acne and problematic skin? Do you like looking like you have a creepy OCD problem? Oh you do? Oh, okay than, as you were....
You have no idea how much bacteria you are moving around on your hair and face.
5. Slouching.
For most people, bad posture is something you can avoid or correct, but our generation, our world is surrounded by doing things the lazy way. Cars allow us to put our seats down so we can "relax" but all it is doing is throwing spines out of place. So put them up, sit back in your chairs, couches, because better posture means you'll be able to breathe easier, that you will (for the most part) avoid back pain, better sleeping patterns, can possibly avoid sciatic nerve issues, and it isn't sexy, at all.
6. Laying on your left side vs. laying on your right side.
Lay on your left, it's better for you. When you lay on your right, you are actually putting a lot of weight on your Great Saphenous Vein which reduces blood flow (especially scary when you're pregnant due to increase blood production and risk of producing varicose veins)