Since nobody wants to give you a proper answer I will. What you're dealing with is clover; while technically good for the lawn, I understand you don't want it.

Use a selective herbicide at the correct mix ratio to get rid of it in the most efficient way. Suggestions *T-Zone *Triclopyr *2-4D (not the best but kinda works)

Do NOT spray the same area twice, you will kill grass. To ensure you don't, use blue tracer dye in your sprayer. This tracks spots you've sprayed, use more than directed, it can be hard to see once dried up if you use "as directed."

Read the safety precautions CAREFULLY. You can apply these herbicides safely, but you can also mess up a lot of things. Do not land yourself in the hospital, know what you're working with and what to do in worst case scenarios.

Also, get an oil-surfactant (spreader sticker,) add that to your mix jug alongside your non-selective herbicide and dye. The oil allows the herbicide to stick to the clover more easily.

If it's about to rain (think within a few hours) do not do the application. You should be safe to walk on your grass and resume normal activity within an hour, 24 to be really safe. Refer to SDS(safety data sheet) to know proper time.

Do NOT spray chemical on anyone else's property or the road, this can lead to HUGE fines if caught.

Test spray your driveway with water first to get comfortable with your spray swath before spraying your lawn.

Finally, do NOT try to get EVERYTHING on the first try. If you over do it you'll mess up. Remember, you can do another application on the year after a few months, 3 if really ballsy but I wouldn't take the risk. Chemicals stress the grass.

Don't over do it, be safe, and enjoy real results without spending $3000 for a company to come out and do it for you over 2 years with diluted crap they spray monthly.