1.Toffee bits - you can make your own if you wish or buy them in the grocery store, Heath makes a good one (they call it "brickle") and they can be found by the chocolate chips in the baking aisle.
2. When cookies come out of the oven I have a crazy habit of tapping on top of each one with a few fingers (very lightly, cookies are hot!), it helps the dough collapse and then you see all the mounds of what is underneath the dough. Its totally optional and does not affect the flavor.
3. If salt is not your thing on a cookie you can omit it (but I wouldn't :-) ).