There are a lot of intensifier in Chinese, like 很，真，挺，非常，相当，极为 ，太，and recently I found out about 蛮. So how can I use them effectively? In particular I want to compare the differences in degree of intensity. I obviously forgot to mention other intensifiers, if possible, please add them in your answer.
- 很 - very
- 真 - really
- 挺 - pretty
- 非常 - >= very, < extremely
- 相当 - quite
- 极为 - extremely
- 太 - too
These words are describing a 'level'. 挺 = 蛮 = 比较 < 很 <= 非常 = 特别 < 极为
太 is somehow special, means it is much more than you expected.
鞋太大：The shoes are larger than your size, regardless of whether your feet are large or small.
I'm answering this question by my sense as a native Chinese speaker.
蛮 is not that commonly or widely used in north China. (but people all can understand), maybe southern Chinese prefer to use it. And I believe it is widely used in Taiwan.