after remove carpet from hardwood floor

I have removed carpet from hardwood floor. I probably need to sand the
floor first before painting.
What kind of sand paper do I need? and after sanding what kind of
filler do I have to use for
the first paint. I am new in this, like to do it by myself.
Would anyone please guide me step by step.

If you're going to go through all the trouble of sanding the
thing down, (A) you shouldn't need filler, and
(B) Why then are you painting, instead of using
stain/varnish/shellac/polyurethane on a hardwood floor?

If you are going to paint, then
(A) Use tinted primer, and
(B) Do *NOT* believe the printer cure-time on the
can. It will dry to the point where you
can walk on it, yes, but it won't cure enough
to stand up to hard use for about a month.

Go to the this site with your web browser:

It will pretty much explain everything you have asked about........ :-)