Under Tools → Customize → Keyboard you can see all available keyboard shortcuts and even define new ones. To quickly insert characters or objects you can use AutoCorrect (Tools → AutoCorrect → AutoCorrect Options) and AutoText (Tools → AutoText): the first one replace short texts by others (like :--: turning into an n-dash) while the other insert arbitrary content (like typing fn and then pressing F3 to insert a table with a Math object and a number range).