Dandelions and thistles can be a big problem here are a few things that can help.
To have a weed free lawn I first focus on the lawns health. The healthier the turf is the harder it is for weeds to grow. Some ways to have a healthy thick lawn are to fertilize on a regular schedule, water the right amount at the right time, weekly mowing as to not cut off to much grass at a time which stresses the turf, as well as dethatching and aeration.
Although a healthy lawn certainly helps, some weeds will still get in. If you choose to spray them yourself you can purchase products at the hardware store just be sure to get the ones that only kill broadleaf not the grass.
If you choose to hire us we have a 5 step lawn treatment program that includes fertilization, weed control, as well as fall rodent repellent. We have had a lot of success with this program and it really helps keep lawns green, thick, and weed free.