[TargaTony]

The best way to do it is to feed from the meter to the transfer switch. The transfer switch will be feed (line side) from both the generator and meter. The load side of the transfer switch will now feed the panel.
If you do not want to do this... Your other option is to feed the generator from a 2 pole xx amp breaker. this can be very dangerous! the main breaker must be shut off if the generator breaker is feeding the house or you will have a BIG problem.
They make a item called a Kirk Key Interlock. This device only allows one of the breakers to be on at a time. It is like a key switch that is only accessible if one of the breakers is in the off position.
Hope this helps!