You must speak more in English. That's the only way to really improve oral English. Speak to the mirror when you brush your teeth. Speak to your pet dog when you play with her. Speak to any sympathetic human you can find. Practice makes perfect.

1, Oxford (the most authoritative brand for advanced learner's English dictionary) 2, Longman (my personal favourite English dictionary, more comfortable than Oxford) I wouldn't recommend Collins Cobuild, or Cambridge, but Macmillan might be another good choice for you. 另外，我建议你使用【学习型】词典（先不要用【阅读型】），一般都会标有【For Advanced Learners】(高级学习者用)。推荐你买本【朗文当代高级英语词典（英汉双解版）】。 http://www.fltrp.com/scrp/bookdetail.cfm?iBookNo=4635&sYc=1-1（点击）

Speak more.. Italki can help you in getting more and more people to speak to. Apart from speaking, you can also try singing along to English songs. It helps..

italki is free! Why not use it?