Gas and Oil Home Heating Furnaces - Natural Gas Furnace has no "tick, tick, tick"

I don't have all the information I would like to post, but maybe I could get some info on what to check first and what to look for.

It's starting to get cold at night here in North Carolina and I remember the heat working at least once this winter, but now it seems to be broken.

It is a natural gas furnace. I hear the relay kick in, then the small fan kicks in, then were I would usually hear the electronic ignition I hear nothing, and after a bit the blower turns on and blows cold air like nothing is wrong.

So it appears I have no spark to light the furnace. What should I check first? Is it smart enough not to turn on the gas if it does not light? I assume the main burner valve is controlled by heat from the lighting flame.

I'll try to get you the brand and model when I get home today.

No spark could be for a few reasons. If the inducer fan prover is not sensing fan operation, it won't even bring the ignition sequence into the picture. That could mean that the discharge pipe outside the house is blocked by an obstruction or that the prover switch is stuck or defective. Usually they get stuck. If you have an external one it might look like a silver pancake. It should have at least one small rubber hose connected to it and going up to the fan housing. You can try jumping across the two terminals on the switch and running the furnace through a start up sequence again. If it lights, the fan prover switch or inducer fan is at fault, or the discharge is blocked. If it still doesn't spark, the problem is in the ignition circuit.