Vocabulary Builder 101: How to Use the Dictionary Correctly
It's often the case that even though a person is genuinely interested in vocabulary improvement, following the wrong steps can prove rather detrimental to their efforts. One common mistake people make is not using their dictionary and other references correctly.
Assuming you already found the word you're looking for, the next step is enriching your knowledge of it. There are certain word aspects you need to familiarize yourself with in order to be able to say "I know what this word means." These include, but are not limited to, the following.

Pronunciation and Spelling

To use a word correctly in conversation, you'll need to know how it's pronounced. When using a word in a written document, you must be able to spell it correctly. Keep in mind that there are sometimes variations between British and American English in both spelling and pronunciation.

Derivatives and Related Words

Take a minute to read about the important derivatives of the word (for example, group the noun "excellence" with the adjective "excellent" and the root verb "to excel"). In this way you don't just learn one word at a time, and it will be easier to remember the related words.

Special Uses

You can't say you know a word when you cannot use it properly. Learn any phrases, idioms, or jargon, the word might be used in.
For instance, you know what "debt" means, but you cannot decode the idiom "pay one's debt to society" solely based on its definition, because nothing in the word "debt" denotes "to serve a sentence, usually in prison" - which is what the idiom means.

Synonyms and Antonyms

An adequate knowledge of a word means knowing at least a few synonyms and antonyms. This is what will bring variety, depth, and color into your speech and writing. You can create your own mini thesaurus with vocabulary lists of new words as you learn them.

Application

Don't just read the information about a word, apply it. Pronounce the word a few times, practice writing and spelling it out, and most importantly use it in context. You can form your own sentences that clearly highlight the word's meaning so that you're sure of the word before you try it out in conversation.

Perspective

Putting a word in perspective sounds rather common sense, yet most fail to do so. Explore the word in depth, discover its related words, the class or category it might belong to, etc. If you categorize the words you learn, you'll be able to retrieve and use them appropriately.

Online vs. Printed Dictionaries

The abundance of vocabulary software and online dictionaries make the use of conventional printed dictionaries rather obsolete and time-consuming. An online dictionary will give you more than a printed one, in less time and effort, but it's still good to have a print dictionary to take with you when you don't have computer access.
If you don't already possess a decent dictionary, you can opt for a cheaper alternative by buying vocabulary building software which features a dictionary among its many other tools.
Pay attention to the aspects of word learning outlined above, and you'll be able to get the most out of vocabulary learning. If you faithfully seek the information on each new word, you'll definitely make vocabulary learning an enjoyable process.