Answer:
I am the first you ever saw, what greets you every morning and what goes out in the end.
What dentists battle on a daily basis
A mechanism to discover who is following you.
I am always hungry, I must always be fed. The finger I lick will soon turn red.
If the day before yesterday is the 23rd, then what is the day after tomorrow.
It weighs next to nothing but no one can hold it for long. What is it?