Grass and trees are the main parts of a yard. If either of these shows signs of problems, the yard can look unkempt or sick. Trees can contract diseases, and grass can be infested by insects or weeds. Treating issues as they come up is best so that you aren't overwhelmed with a lot of tasks at once.
Adjust soil pH as needed. Check the pH level of the soil in the lawn. Compare that to the optimal pH level of the grass you grow. Most grass prefers a soil that is just barely acidic. Add fertilizer to the soil to adjust the pH balance if necessary. Add fertilizers each year when needed.
Aerate the lawn each autumn. This will break up the soil and give it air. You also can rake the lawn to de-thatch older grass and break up layers of dead blades and growth. This will bring in more light and give new growth more opportunity to make it to the surface.
Water the lawn in the early morning. That allows the water time to soak in before the heat of the day evaporates it. Do not water in the evening. After the sun goes down, leftover water that cannot be absorbed will sit in the dark and cause mold and mildew problems.
Cut the lawn at a level recommended for your type of grass. Some grasses have a range of heights from which you choose. Pick near the lower end of the range if you don't mind cutting the lawn more often, and the higher end if you want to wait longer between cuttings.
Add an overseed in the fall to fill in spots of grass that are thin. Add a grass that will not take over the lawn and choke out your main grass. An example is rye.
Rake dead leaves as they fall from trees. This will keep mildew and mold from spreading.
Trim dead and diseased branches from trees. Use a tree trimmer to trim each branch at least 1 foot below the problem.
Trim branches for shape. Some trees don't need help with this and are naturally shaped. Some timber trees, however, need help. If you have one of those trees, look for branches that are longer than the branches below and trim them. Also cut one of the main trunks if the top of a tree has formed a fork. A tree with a forked top is weak.
Provide moisture. Trees may need watering during a drought and if newly planted. Keep soil damp, not soggy. Add mulch around trees to trap in moisture. Do not put the mulch up against the trunk of trees. Keep it back several inches.