You might remember the meaning of the character 疏 with this easy mnemonic:
The thread on this bolt of cloth (疋) is very sparse. Take the lid (亠) off the private (厶) box I keep open there and bring me a knife so I can slash (丿) a line (丨) through this thin cloth.
Using mnemonics to remember the meaning of Chinese characters like has a huge impact on how long to learn Mandarin it takes.