The following are also some book references to help you improve your oral English:
- Spoken English by R K Bansal and J B Harrison
- Pronounce It Perfectly In English by Jean Yates, Barrons Eductional
- English Pronunciation For International Students by Paulett Wainless
Dale, Lillian Poms.
As for remembering the words you need to practice a lot ,the more you practice ,the more you will be able to use the words in their right context.
Lots of reading , chatting, exercising, listening and speaking will help you use the words efficiently and with lesser mistakes in structure ,grammar and pronunciation.
It is a gradual process and if you practiced on a continuous basis with real dedication you will sense a tangible progress and improvement sooner or later depending on your efforts.