When using ellipses and em-dashes, here are a few tips:
Ellipses run into the next word, whether they are in the same sentence or not, unless you're using dialog.
The cat was sneaky...and persistent when it came to getting the people's dinner.
The cat ate everything he could...He even devoured salad.
The cat talked in a mumble... "Rawl, raaawl..."
Em-dashes are made by typing a letter, then adding two dashes. - and -
Then you simply add another letter.
Something I see a lot with em-dashes is a backward quote. You can fix this by typing the em-dash, then a letter, then the end quote and deleting the letter.