Trouble with learning vocabulary

Indeed, some words are more difficult to memorize than others. How could that be? First, some words have more than four vowels. If they are easy to divide into common roots, they would be remembered quicky, like transportation. Otherwise, it would take more time. Second, words that have different prounciations or are hard to pronounce also take more time to learn the spelling. Finally, I think words which are not used in a common way or in daily life are still hard to know or write down.

In my case, when I encounter these situations, I'll practice more time, no matter to read or to write them down. Especially I'll write one word on a paper, making the words fill in the paper and trying to write beautifully. If I have more leisure time, I'll connect them to other words and read the examples, in order to remember new vocabulary deeply.