I'm not a native speaker but I've been studying Chinese for three years, during which I adopted and improved my own way of studying Chinese.
I'd say first of all that even if they tell you that you must be young enough to become fluent in any language, it's only partially true: you see, there is a say in 'language acquisition' that goes "younger is faster, older is better"; so your chances of getting good on Chinese are not based on how old are you, but instead (and most importantly) on how much comprehensible is the input of Chinese.
In short, you just need to start from the basics even with the material you make use of, like starting with a Chinese cartoon for children, otherwise you might fall in what linguists call 'interference', which is incredibly variable and brings advantages half the time.
Last but not least, it has been demonstrated that learners of a foreign language so different as English-Chinese tend to learn slower than someone who is learning say English-French, but they improve faster over time (for me it was two years).
Now that I rambled for too much, even I wish to know more about suggestions for improvement from native speakers ^-^