You can actually create your own keyboard shortcuts for inserting other special symbols in Excel such as the micro symbol (µ), delta symbol (∆), degree sign (°), plus-minus sign (±), common superscripts such as ² or ³, common fractions such as ¼, ½, ¾, dot sign (·), partial differential (∂), infinity (∞), etc.
To do this in Excel, go to Tools > Options > Spelling tab > Autocorrect Options button > Autocorrect tab. Add the entries in the table listed below. Because the Autocorrect options apply to the other Office applications, you'll find that after you add these using Excel, you can use the same shortcuts in Word, PowerPoint, Outlook, etc.
Replace: With: (micro) µ (delta) ∆ (deg) ° (degree) ° (+/-) ± (^2) ² (^3) ³ (1/4) ¼ (1/2) ½ (3/4) ¾ (dot) · (part) ∂ (partial) ∂ (inf) ∞ (infinity) ∞
Note that not all of the unicode characters will be displayed correctly on other computers.
By the way! If you ever want to undo when Autocorrect makes an unwanted change, such as when you really want to use (c) for the copyright symbol and not ©, right after Autocorrect changes the text, press Ctrl+z to undo and go on typing.