i have been taking chinese for... 8 years now?
1) dont half ass it like everyone said, i did and i really didnt, its like skiing your foundation and fundamentals will help you out.
2) it is extremely difficult, remember, you have characters, pinyin, and english meaning of Chinese.
3) tones. These have fucked me. with so many characters things that sound the same mean totally different things. like ma. means mom, question word, and horse.