Look at the context of a word, and see if this provides you with clues, according to Cuesta College's academic support. For example, if you see that a word is capitalized, then chances are it is someone's name or the name of a place. Otherwise work out what the general meaning of the sentence is, and this will give a clue as to the meaning of the word.
Look at the words around the mystery word. Often in a literary work, there will be direct synonyms or antonyms around the word. For example, in the sentence "He climbed the mountain until he saw the peak, the zenith." Although you may not understand the word zenith, you can guess that it means the same as peak.
Break the word down into different segments. If it is a longer word, then the prefix or suffix will give a clue as to its meaning. For example, the word "extraordinary" contains two segments, "extra", meaning outside or beyond, and "ordinary", which means normal. Extraordinary means beyond what's normal.
Consider words which have similar segments to the word in question. The word "philanthropist" may be a mystery, although think about words such as "philosopher" or "philanderer" and you conclude that a "philanthropist" is someone who has a love or keen interest in something.
Look the word up in a dictionary if you cannot work out the meaning yourself. If you want to challenge yourself, look the word up in a thesaurus, which will give you synonyms. This will help you to link it with existing words in the dictionary, and give you a broader vocabulary.