Cool season weed seeds are germinating in their thousands (or should that be millions) and one of the easiest times to get rid of them is at cotyledon or two leaf stage. This is the stage when they first burst through the soil and develop their first set of true leaves and are most vulnerable to control. The safest and easiest control is smothering seedlings with composting or chunky mulch before they establish themselves. A layer of mulch will block out much needed light to the seedling and it will wither very quickly.  Spreading mulch early saves hours of back breaking work later on in the season.