Here are a few strategies for you to try on your lawn.The very best weed killer for lawns is prevention
Each type of grass or turf you plant has an ideal cutting height for good growth and health. This cutting strategy and and cutting before it gets too long . The grass will pretty much always out grow weeds so they get no foothold in your lawn.
This always works well with a good watering strategy and fertilising of your lawn. Lawn cutting needs to happen when the lawn is one third fighter than the ideal height. In the height of summer that might be once a week. In winter or slower seasons every 2 to 3 weeks. Of course weather conditions are always a variable.
All gardeners face the problem of weeds and how to deal with the ones that crop up everywhere in your pathways, lawns, garden beds, and even in pot plants. I do suggest you try organic weed killers before the more dangerous herbicides.
Poor light or soil can make it impossible to grow good lawn. But if you cover bare soil opportunistic weeds will invade and take hold. Mulch is always a good answer in these areas. or dense plantings of those plants that grow in shaded areas.
Weed matting is also useful to place under mulch for the more difficult areas where weeds have a hold. (Tip: use proper weed matting not black plastic, as black plastic will kill microbes in the soil)
Consider a barrier if you have kikuyu or bamboo that has a very thuggish way of invading your garden. Takes time in the beginning but worth the trouble. Use deep boarders of wood or corrugated iron.
Hand weeding is a great option using your hands with hoes or forks. Do this regularly while weeds are small and not too hard to remove.
Herbicide sprays can always be used but remember to wear protective clothing at all times that includes gloves long sleeves long pants boots mask and protective glasses.
There are organic sprays on the the market. Research at your local garden centre.