You can remember the meaning of 下手 with this easy mnemonic:
Mandy was all ready to have her ears pierced but her friend was slow <strong>to start</strong> the process. The friend carefully grabbed Mandy's earlobe from <strong>under</strong> (下) with one <strong>hand</strong> (手) and held the ear-piercing gun with the other.
Using mnemonics to remember the meaning of Chinese characters like can have an enormous impact on how long to learn Mandarin it takes.