To move the insertion point to the beginning of a word document or to the first cell in an excel worksheet, use the keyboard shortcut

Ctrl + HOME

Explanation:

Pressing 'Ctrl' key followed by the 'Home' key (Ctrl + Home) will move the insertion point to the beginning of a Word document. In an Excel worksheet, this same keyboard shortcut ( Ctrl + Home) will move the insertion point to the first cell.

PS: Ctrl + End will do exactly the opposite. It will move the insertion point to the end of a word document or to the last cell in an Excel worksheet.

Hope this helps!