The dandelions are starting to flower and this is the best time to pull them.  Tools for pulling weeds are available at most hardware stores.  Pulling dandelions when they are flowering will result in about 80% of them not returning.  At this time the plant is putting alot of energy into flower and seed development and is expending alot of its stored food for this developement.  This is your best natural way of dealing with a dandelion problem.

Orgainic Weed Control

Mechanical Weed Control