Getting rid of weeds?

Ok we have a small garden with borders but I have mostly broadleaf weeds growing this year over most of the lawn. I am considering a 2, 4-d herbicide. My questions are which are the best ones and some general guidance on dilution and usage for usage when the grass is inactive.

 

When you use a weed killer the weeds should be actively growing, the fact that you want to use it when the grass is dormant suggests you want to use it late or early in the year, the weeds will also be dormant at that time.