Generally timing is an individual thing really. However there are some good guidelines. If it's a stock motor try aiming for 8 - 10 degrees, don't pull the apprentice move and leave the vaccuum advance on, and then just play with it. move in 2 degree increments till you get the most power.
Lot's of mechanics will tell you that you can set it by ear, just listen for the motor to 'ping' and then back it off a degree or 2. Either way has worked for years.
PS if the timing is really, really, really off, maybe your timing chain jumped, or you have a vacuum leak.
Either way now you should know where to start.