Read. Start with books at your level of reading difficulty, and move on to reading everything, including cereal boxes, newspapers, magazines and the instructions that come with that bookshelf you want to add to the den. Reading is hugely important in learning how words are formed. Regular reading of books will expand your vocabulary and improve your spelling.
Read aloud to others, or read several pages into a recording device. Play back the recording while rereading the material silently. Note any words you may have had trouble with. If you or a listener did not understand a word's pronunciation or meaning, jot it down to refer to and check later.
Write down any words you do not recognize or know the meaning of. Write them on index cards or sticky notes and place them on your desk, refrigerator or mirror. Study the word. Sound it out by breaking it down into syllables. Speak each syllable distinctly and put them together slowly. After several soundings aloud while viewing the word, speak the word at a normal rate of speed.
Look up the words you don't know in a dictionary. Notice how the syllables are broken down. Phonetic spellings of words may accompany the definition. These are useful to understand. Practice saying new words aloud while viewing the written version.