I've used corn gluten meal for years as a pre-emergent and it works fairly well. It's not perfect and the more you apply (I use about 20 lbs. per 1000 square feet), the better it is at controlling weeds.
You have to accept that there will be some weeds. Not a yard-full like some neighbors, but the occasional weed on a regular basis is easily remedied through hand-pulling and keeping your grass height above 3".
Unfortunately, a lot of folks want that "18th green at Augusta" look to their lawns, hence the annual C-130 flyover with a load of Agent Orange being dumped, most of which finds its' way into the groundwater or nearby creeks, streams, etc.
For stubborn weeds, I have the FAC hold off on the Herc and I use something called "Burn Out." Nope, it's not a John Force product. It's clove oil and a couple of other "natural" goodies that work well against weeds.
However, it's non-selective, so focus on the front sight when you use it!