You're going to have to actually put some real effort into this. I know it's a drag, but it is what it is. The best way is to till the dirt,pick out any weeds you see, wait a few days, repeat the process, wait a few days, and repeat the process again. This gets rid of the weeds and then kills the new ones just germinating. It's pretty much an on going thing. There is no such thing as a weed free garden. It has to be worked at. If you dont have a tiller, then you'll just have to do it the old fashioned way and pull by hand or use a hoe.
As far as poisoning the weeds goes... Why would anyone want to ad poison to the earth. Besides that, it's a short term solution. As the previous poster noted, you'll still have to pull the weeds out. Then you'll have to keep repeating the process. Not to mention the expense of buying the chemicals.
Once you've gotten rid of the weeds and planted your garden, take the time and spend the money to mulch it well. This will drasticly slow down , if not prevent the weeds from returning. The added bonus to this is that it will protect your plants from the high summer temperatures, will save water and will condition the soil (assuming you use a natural mulch, such as shredded tree bark, hay, etc)
Good luck and happy gardening.