The trick is to understand that it's a two step process. Let me explain.
1: Developing a word bank
2: Application
I was wondering what would be good tips to improving my Vocabulary.
Read read read. Keep reading. Online journals, essays, etc. Any "intelligent" text is bound to have a plethora of words. You could also sign up to a dictionary.com word of the day or something along those lines.
How do they articulate their words so coherently.
This is where the real marks are awarded. Examiners hate it when students write pretentiously in their essays. Whatever you do, DON'T throw in a few big words here and there. It's all about consistency and meaning. If your essay becomes convoluted with unnecessary words it's likely that marks will be lost. So my tip for the application is WRITE WRITE WRITE