how do i tap my home phone?

Some answering machine allow you to record a phone con.  They do lay
down a beep on the track so the other party knows you are recording.

Legally phone tapping is illegal. in some districts in US one party
consent is mandatorily required in few other states even that is
banned. first of all to tap a phone you need a investigator warrant.

Yes, partha, in some states to record a telephone conversation between
two people, even if it is your own phone, and neither knows it, is
illegal.  However, that has not always been true in all states.

In the 80's, I did legal research in the area covered by N.W.2nd, and
one state had such a case. A wife and her lover conspired to kill the
husband, using his telephone, and the defense attorney's tried to
exempt use of the recording due to such tapping laws. While I forget
which of the states it was, that state's supreme court ruled that the
recording could be used, due to the gravity of the case, and the fact
that it was his own phone, not someone else's.

You will definitely need to consult an attorney in your state for current status.

At one time, Radio Shack sold a small control which would detect any
phone on the line being raised, and would start an ordinary cassette
recorder in record mode.  If they still sell such a device, you are
responsible for using it in compliance with local laws.