One of the major study tips are understanding what you learn. But when you learn a new word, how do you understand it without memorization?
Use the word in context, diurnally if necessary, until it's part of your lexicon.
That's the expedient way to foster development of a sesquipedalian vocabulary.
I assume your question is about learning foreign words?
Understanding is important when learning concepts and ideas. When you understand something (or if you experiment or play with newly learned stuff for that matter) you make connections between the things you've just learned and things you already know. The result is that you will remember the newly learned things better.
The same goes for learning foreign words. It's not so much that you need to 'understand' a word, it's linking it the something you already know so you'll remember it more easily.
For example, learning the French word for explanation, which is 'explication' is probably not very difficult as the two words are rather similar. However, you might have some trouble remembering the Dutch translation, which is 'uitleg', because this word is totally different from the French and English word. Without more knowledge of the Dutch language you cannot link it easily to something you already know. However, even in this case you can use a 'tric' to remember the Dutch word. Image a pirate with a wooden leg explaining your something. This image will link the last part of the Dutch word (leg) with the word explanation. This is called the LinkWord technique and is one of the many mnemonics you can use for learning words.