想 (xiǎng, "to think, want, miss") breaks into two parts: 相 (xiāng) on top and 心 (xīn) at the bottom.

心 means "heart," and it's the meaning component here — thinking and wanting are heart/mind activities in Chinese character logic, the same reason 忘 (forget), 念 (miss), and 情 (feeling) all carry 心.

相 itself is 木 (tree) + 目 (eye), and it originally meant "to look at, to observe" (as in 相片 xiàngpiàn, photograph — literally a "looked-at image"). In 想 it mainly supplies the sound (xiāng → xiǎng), but a workable mnemonic is to treat it as meaning too: picture yourself gazing (目) at a tree (木) with your heart (心) — daydreaming, longing, thinking something over. That image ties all three pieces together and is easy to recall even though it's not the strict etymology.

A sentence to anchor it: 我很想你 (Wǒ hěn xiǎng nǐ) — "I miss you a lot." Note 想 covers both plain "think" (我想这是对的, I think this is right) and "want to" (我想去, I want to go), so context decides which sense is meant.