I think you need to decide which element of your English needs to improve first – don’t try to do everything at once. Personally I have found that people in business really want to improve their spoken English more than anything else. Fluency in English is a good selling point when you are trying to get a good job.

With spoken English you need to improve your speaking AND listening skills. Do you ever listen to talk radio? Plays on Radio 4 etc? To gain fluency in comprehension and expression you must get out and talk talk talk! – preferably with native English speakers. Expose yourself to as much spoken English as possible – including films/tv.

Learning hard words from the dictionary is very worthy but learning vocabulary in isolation (not in context) isn’t very helpful.

Good luck – keep talking and listening!

(Studying/practising little and often is a good habit to get in to …. an hour a day every day perhaps?!)

http://www.google.com/search?hl=en&q=how+to+learn+english

http://www.google.com/search?num=20&hl=en&safe=off&q=how+to+learn+spoken+english

However, if you can enroll in a class, you’ll probably learn quicker. Look around your area for any resources that might be available to you. Are you in the U.S? If so, open the phone book and call your local library and ask them if they know of any community resources. Also call your local community college regarding English classes. Contact the university you attend and ask them if they offer any English as a Second Language classes. The international students office might also be able to help you. Good luck.