Knowing the name of your weed is helpful in choosing a weedkiller, but it's certainly not a requirement.  In fact, there are three pairs of questions you can ask yourself about any weed.  If you answer those three pairs of questions correctly, you can choose the appropriate herbicide.

This is one of the Most-Asked Questions that we have archived at our website. Click here to see it.  (Oh, and by the way, dandelions are cool-season, annual, broadleafed weeds.)