If you are uncertain as to which mark is which on the crankshaft pulley, determine Top Dead Center (TDC) as follows:
Remove the #1 spark plug.
The #1 cylinder is on the right side, closest to the front of the car.[/mark]
Remove the distributor cap and find the small notch on the rim of the distributor body that marks the position of the #1 spark plug wire (5 o'clock for SVDA distributors; 7 o'clock for 009 distributors).
[mark]This is a very thin little notch in the metal - it's easiest to find if you run your fingernail around the rim of the distributor body.[/mark]
With a 19mm socket or 19mm box-end wrench (ring spanner) on the alternator nut, rotate the engine (clockwise -- the way it goes) until the rotor is approaching the #1 spark plug position (the notch you found in the rim of the distributor). This will place the piston near the top of its stroke.
Insert a pencil (eraser end first) into the #1 spark plug hole until it rests on the top of the piston.
[mark]Make sure that the pencil is horizontal, not crosswise of the cylinder. If you're not careful, you make break off the end of the pencil, which will then fall down into the cylinder![/mark]
With the 19mm wrench (spanner) on the alternator nut, and while holding the pencil on the top of the piston, move the crankshaft back and forth across the #1 spark plug position until you find the point at which the piston is highest in the cylinder (i.e., the pencil is at its furthest point out of the spark plug hole). This is Top Dead Center.
[mark]It is important to get the piston roughly at TDC (TDC mark near the split in the crankcase -- Step c. above). Then place the pencil in the hole and rock the piston back and forth to find the center of the no-movement position. If you put the pencil in with the piston at or near BOTTOM of its stroke, and place it so that it is sitting at an angle across the cylinder (the spark plug hole is on the upper side of the head), then rotate the crankshaft, the piston may push the pencil sideways break off the end. Removal of this end bit of the pencil is expensive!
On the crankshaft pulley, with piston #1 at TDC, make a mark (with white paint) exactly opposite the split in the crankcase. This will be your TDC mark and the starting point for other timing marks you will make. You will find the timing mark(s) that apply to your configuration by carefully measuring from the TDC point around the rim of the crankshaft pulley.
While you're at it, rotate the pulley 180 degrees and paint a mark on the pulley there. You will use this point when you adjust the valves (this is the point at which pistons in cylinders #2 and #4 are at TDC).