One thing that fascinates me in Mandarin is the number of times you see a word repeated in a sentence. This can commonly occur with adjectives.
The simplest example would be a single character adjective that is repeated.
她的脸红红的。(Tā de liǎnhóng hóng de.)
This literally means "her face red red" or more likely "she blushed". But the word for red 红(Hóng) is repeated, in this case for emphasis.
Instead of saying:
你的眼睛真大的。(Nǐ de yǎnjīng zhēn dà de.) which says "your eyes are really big",
you get a similar effect by doubling the word for big:
你的眼睛大大的。(Nǐ de yǎnjīng dàdà de.)
Now where the fun begins is that many adjectives involve two characters, and instead of A becoming AA, the effect is that AB becomes AABB. (Not ABAB)
高高兴兴 (Gāo gāoxìng xìng) where 高兴 (Gāo xìng) means happy.
漂漂亮亮 (Piào piàoliang liàng) where 漂亮 (Piào liàng) means beautiful.
I'll write more soon on the best methods for learning Mandarin. If you want to get a taste for it in the meantime though, my current favorite site is iTalki, and my favorite teacher by far is Amy He. If you decide to try it, click here and it's cheaper for both you and me.