1. USE WORD LISTS
One great place to look is at www.manythings.org, where they have vocabulary lists on animals, body, body care, books and things to read, buildings, business English, etc.

2. USE FLASHCARDS
One way is to make cards yourself, which is actually an excellent way to learn words as you can repeat them whenever you have some free time. Another option is to use flashcards that are available online.

A wonderful site for that is http://quizlet.com/, where you can add the words in English and your mother tongue. One fantastic extra feature here is that after you have saved your list pronunciation appears next to the words. And when your list is created, you can learn the words and even take tests. Quizlet also lets you create groups where you can save your lists and share with friends (you can even add a password).

Another similar site to Quizlet is Studystack.

3. MAKE SENTENCES
There are also some free online dictionaries which allow you to search for sample sentences.

I personally use the MacMillan Dictionary and Your Dictionary.

4. USE VISUALIZATION
Visualize the new word.

5. READ A LOT IN ENGLISH
Reading gives you more confidence and when you see a word or an expression in certain context, you feel more confident to use it yourself. The same goes for sentence structure. Make it easy for yourself to look up new words. Bookmark a few good dictionaries. Here are some:
* www.thefreedictionary.com (You can also listen to pronunciation here!)
* www.howjsay.com - a free online talking dictionary of English pronunciation.

A great feature on the page is Cleverkeys (under Tools), which lets you hear pronunciation even in your Word document or Powerpoint:)!
www.refseek.com/directory/dictionaries.html: a guide to the 30 best online dictionaries.