You will need a journal (any type will suffice) and a pen.

Now, pay attention to your everyday conversation and your commonly used words. Consider them for a moment and use this website to locate matching words with a similar or same meaning (synonym). Write them down in your journal along with their definitions and in future conversations, attempt to implement them by swapping them out with your common words.

Another exercise you can undertake is to pick 3-5 words a week from the dictionary, write them in your journal — along side their corresponding definition and study them. Possibly use them in a conversation to actively remember. You can also make up some flash cards (online, written or printed) in your memorization quest.

I really hope you decide to implement this in your homeschool, if you choose to then let me how it worked out for you!