1 - Bad posture will not help you. With anything. Maybe if you want to look a little shorter.
or like Quasimodo In fact, bad posture can cause a lot of nasty side effects and health problems down the line!
Proper posture, on the other hand, has a whole slew of benefits. It doesn't necessarily help you lose weight directly, but it does facilitate breathing, increase focus, and mentally avail you.
You can read an article about Proper Posture, here.
2 - Lemon water only helps to fight hunger cravings, not make you lose weight. It's another greatly beneficial drink, though, like the green tea we were talking about earlier.
Don't judge me for the Lifehack link.
3 - This... is a technique for digestion. If you want something psychological, try using smaller plates when eating. Even if you eat the same amount, it'll trick your brain into thinking you've had more.
4 - Now this one is actually pretty valid. Stress is a real cause of weight gain, and can actually block you from losing any. Remember that the mind has power over the body, and you have power over the mind.
5 - What? There are a lot of weird chemicals in some types of gum, that's true, but I don't think it would have that much of an effect. I mean, stop chewing it, sure! It's kind of an annoying habit, most gums have addiction forming chemicals in them, and it's (arguably) not good for your teeth. But unless you're having some sort of negative allergic reaction of some sort, chewing gum will neither make you gain weight nor lose it as far as I know.
6 - Walking is a good exercise, and does burn calories, but isn't a get thin quick plan. A general rule of thumb would be that a person weighing 160-180 pounds usually burns 100 calories per mile. That's a lot of walking if you're aiming for the 3,500 calories, 1 pound per week method.
Thinking about that, though...
Something else a lot of people fail to take into consideration about weight is that it might be from your heritage. No, I'm not saying that a chubby grandfather screwed you over. But if you're from a strong bloodline descended from vikings then you're going to be a bit larger if you're healthy. It's just how your ancestors adapted to live. You should do some ancestral research, and consider what things should and should not be in your diet.
And don't forget to take everything on the internet with a grain of salt. It's never better than consulting a Physician, Dietitian, or just using your good ol' common sense.