Every lawn is going to have some weeds. Here you will find the tips to make them few and far between.
The best defense against weeds is a nice thick lawn. This will effectively keep weeds from having anywhere to grow. If you ever notice, the places where you have the biggest problem with weeds tends to be the thinnest areas of your lawn.
If you have a wide spread weed problem, the best option is a broad leaf weed control. This can be applied by itself, or there are many combination fertilizer/weed controls.
The other important step in dealing with a wide-spread problem is overseeding. This will help thicken your lawn eliminating room for weeds to grow.
Ideally, you will have sporadic weeds throughout your lawn. This is almost unavoidable, and is best dealt with using a targeted spot weed treatment. This minimizes the chemicals you spread over your entire lawn and is just a better practice in general.