There are plenty of books (recommend Les Andrews book) with all the complicated steps on Model A timing. They are important to be sure. These instructions will presume those have been done and/or are considered to be correct. Maybe you just pulled the distributor and did not mark position or the timing was previously set wrong. This will get you going.
One item you should check is the points. The gap should be set to .020 inches using a feeler gauge. Do not use a dime, matchbook or other substitute. Feeler gauges should always be in your toolkit. As Model A distributors age they get worn and play/movement becomes a problem. In some case the car may run fine, others will run rough and some may not run at all as the point gap will be inconsistent. It is important to check the gap for all four cam lobes to indicate these problems. You may need to set an average gap setting for all four to get going temporarily. If that is the case your distributor will need a rebuild or replacement.
First turn the hand crank until the points are in the fully open position. Set to .020 inches. Turn the hand crank another 180 degrees so the points will open and again be at a fully open position. Check that the gap is still at .020 inches. A variance is indicative of play in the distributor. Repeat this step another two times, checking the points gap. If this is being done in an emergency and you have a large variance, set the points so the average gap on all four lobes is about .020 inches and recheck all four. If the point gap is too far off, the rest of the timing procedures will not work!
By far the most common issue with timing seems to be locating Top Dead Center (TDC) with the timing pin. You first remove the timing pin and you will want to insert the opposite side of the pin back in the same hole. Keep slight pressure, pushing the pin in. Now hand crank the engine slowly until you feel the pin seem to move in. In some cases the amount of movement of the pin will be a fraction of an inch. Do not expect it to move all the way in on many engines. If not sure try again. It takes two complete revolutions of the hand crank to get back to insert the pin again. The more often you do this the more you will notice the effect. It is equally important to crank slowly so the engine is not cranked past the timing mark. Many people do not realize they have cranked past and the timing will always be off. Take out the number 1 spark plug. You might need to take out all spark plugs to make cranking easier! TDC is when you are at the position the pin is inserted.
Now set the spark lever to the fully retarded position. This is the fully up position. Loosen the cam locking screw. Rotate the cam until it is just (and I mean just) about to open the points for the number 1 cylinder. Now tighten the cam locking screw being sure the cam does not turn and actually start opening the points. The tightening of the screw willmake the cam want to turn further clockwise. Sometimes, having the cam slightly back a bit before tightening will get you to the exact position after tightening.
If you have set the timing correctly you should be able to (with the ignition switch turned on) turn clockwise on the cam locking screw and you should see a spark across the points. You should not have to really turn the screw to get a spark.
If you get a spark as expected then replace the rotor, cap, etc.; remove the hand crank and thread the other end of the timing pin. You should be read yto start the car!