Lawn professionals usually do a great job, but most of the services they provide are easy to do yourself for a fraction of the cost.
Fertilize at least 3 times a year, once in late August or early September, once in October and in spring as the grass starts to green up. If you water your lawn in the summer, also fertilize in June. Apply a weed preventer in spring to keep out crab grass, foxtail and other annual weeds.
It’s convenient to buy fertilizer with weed preventer mixed in so you can apply both at the same time. Few lawn pests are as damaging as grouts, but an application of grub control easily stops the damage before it starts.