How do I use the three "de"s? 的，地 ＆ 得

This is a common question faced by those starting to study Mandarin, and even native chinese speakers sometimes use the wrong "de" in written chinese. Each of these complement characters have many many uses, but here we will just cover the most common use of each one.
Firstly we should consider the most common "de" - 的。 This is a possessive marker - it shows us that someone, or something owns something else. For example "他的鞋子“ His shoes. Here, 他 denotes the person, and 鞋子 the object he owns - therefore we should add 的 after the person in order to signify that he owns the shoes. The possessor does not necessarily need to be a person, nor the possessed thing a physical object - for example, if we wanted to express that an idea is difficult , we could write ”这类思想的困难是。。" - literally, the difficulty of this kind of thinking is。。。
Secondly - 得 - here we will consider what is unfortunately both the most common use of this de, and the hardest for english speakers to understand, as it doesn't really have an equivalent in English. We use this complement to modify verbs, and express some kind of characteristic attached to the verb. For example 他做得很好 （he does it very well)， 别说得太快 (don't speak too fast) 。 We can see that the verb, followed by the complement de, is modified by the adjective - 他 （he)， 做得 (does it) 很好 （very well).
Thirdly, 地 - this is used to modify adjectives into adverbs, and can be roughly seen as the equivalent of the -ly suffix in English. Luckily, this isn't nearly as common as the other two complements we have discussed. We use the structure adj + 地 + verb to express this. For example, 她开心得打扫了 - 她 （she) 开心 （adj - happy) 地 （compliment）打扫 （verb - cleans) - we end up with "she happily cleans"