First, line up the marks on the flywheel/clutch-housing (for #1 cylinder firing). That should be near enough to TDC for #1 cylinder. At that point, the input and exhaust rocker arms should be loose (have a gap). If they both are not loose, either you have poorly adjusted tappets or you are a full rotation off in your firing order.
The engine rotates twice to fire all cylinders - the timing mark comes around twice and you could be 360 degrees off for #1 firing, one rotation off. Just ignore me, if you aware of this - this is a common mistake made when restarting an engine.
If your engine "passes" the above test, then try your timing technique (my guess is that simply setting you engine to the timing mark should not cause your engine not to start).
