Perennials include Canada thistles, dandelions, milkweed, and other species that come back from the root each year. Control measures usually include cultural, mechanical, chemical, and biological. Cultural control usually means having such a good stand that weeds don't get a chance. Mechanically, a mower and spade are still good options. There are a host of chemicals available to control thistles.
Biological controls are also available for some weeds.
Biological control is when we employ a live organism to control another live organism. For instance, there are thistle weevils that can help control the biennial thistle. Now, for specifics. I'm going to emphasize biennial thistle and perennial weed control. Biennial thistles include those large purple flowered things in pastures and roadsides that start to bloom about July.