Create your flash cards. For simple vocabulary building, you can write the English word on one side and translate it into your native language on the other. Alternatively, you can print out pictures on one side and print the word on the other. If using the card for verb conjugation, you should put the verb on one side, and possible versions of it on the other.
Review the flash cards when you have time to study. Look at one side of the flash card and try to say what's on the other side. For example, you may look at the word in your language and then try to say the English word. Occasionally, reverse the side that you look at, so that you start by looking at the English word and translate it into your language.
Color-code your flash cards and use to build sentences. For example, you may want to put nouns on red cards, verbs on green cards and adjectives on yellow cards. Pull out one or two cards of each color and create a funny sentence from the words you've chosen.
Play games with the flash cards. If you create two sets of flash cards, you can match them up in a game of concentration. This is easier with online flash cards. If you have a friend who is also studying English, you can play a game like Snap, in which you have to say the cards out loud as you turn them over and say "Snap" if the same card comes up twice.
Add to your flash card set as you learn new material. As you encounter new vocabulary words, create a flash card for that word. Take out the words that you are confident that you know to make room for these new cards, but remember to review the old cards every once in awhile.