There are several things you can do in your backyard: treat with insecticide, change the layout of the yard, and manage the landscape. You should try to create a tick-safe zone.
In the tick-safe zone you try to make your yard inhospitable to ticks. If you need a target focus on the areas that are most frequently used by you and your household members (pets included).
Ticks likely enter your yard with rodents, deer and other critters. Ticks thrive in shady, humid places, but can move to dryer and even sunny areas when they are looking for a blood meal.
Thus you want to limit moist spaces (for example: leaf litter piles, stacks of firewood) and keep your lawn mowed short.
Areas in your yard treated with pesticides that target ticks (acaricides) can have lower numbers of ticks. Timing, dose, and the active ingredient of the pesticide will determine its success.
Some lawn treatments already include pesticides that kill ticks. You can apply insecticide yourself, or contact a professional business such as lawn care companies or exterminators. The EPA can help you with product safety information and your local health and agricultural office can give you advice on timing.