Use clean hands and tools when handling (planting) the sprout, and don't break anything.

I let the taproot grow to about 3/8ths of an inch in the paper towel. When removing 'em from the paper towel, poke a shallow impression in the soil where you want the seed, and keep the top of the seed at soil level. Bury the taproot, but don't bury the whole seed. (but don't leave it sticking above the soil, either) Don't crush, push on, fold, spindle or mutilate the root. You'll want the soil moisture to keep the seed cover moist while the plant is trying to shed it. Otherwise, you'll end-up having to give it assistance with prying-off the cover on some of 'em. (risking fatal damage)

Once in the soil, do not overwater. Tiny ammounts daily , but only if necessary. Also, use care when you do water. If you add water too fast, the seed can get disloged and 'migrate' deeper into the soil or wash down the sides of the cup. I spray-mist the soil to prevent seed 'migration' and overwatering. No nutrients for a couple/few of weeks, minimum. (4th or 5th set of true leaves)

The 'lighter' and smaller-grained the soil is, the easier it is for the seed to maneuver in the soil. Large chunks can and will stop all progress, and most seeds don't have the 'oomph' to push chunky debris out of the way. (no large chunks above the seed)

In the winter, I keep the lights on for an overnight heat source, but you have to watch the soil moisture closely. Don't let the seeds get too hot or too cold. Especially cold.

Be patient. Depending on strain, soil, temperatures...it can sometimes take 10 days or more to get the sprout to break-ground.
About 7 or 8 years ago I was gifted some White Widow testers. I put 'em in soil (twas before the paper towel method existed) and patiently waited two weeks before deciding I had screwed-up somewhere down the line. So I tossed 'em in the trash, soil and all. A few days later I was tossing out the trash, and found all but one had sprouted, stretched, and died in the darkness of the trash can.

Good luck. :thumbsup: