You can remember the meaning of 明天 with this easy mnemonic:
Tiana was a <strong>bright</strong> (明) little girl who loved watching the clouds in the <strong>sky</strong> (天). She could see so many animals from the changing shapes of the cloud. When the day ended she looked forward to <strong>tomorrow</strong>.
Using mnemonics to remember the meaning of Chinese characters like can have an enormous impact on how long to learn Mandarin it takes.