First, you’ll need to analyze the cause for your yellow or brown patches of grass. If your grass isn’t getting enough water, perhaps it’s time you considered installing a lawn sprinkler system. If your pet’s urine is the culprit, try to encourage your pet to relieve himself elsewhere in the yard. If pests or fungi are the issue, there may be pesticides or fungicides that could be applied to the area. You should rake up grass clippings after mowing the grass or piles of leaves and other debris as needed, as many pests tend to hide in these piles. If your lawn isn’t getting enough sunlight, consider thinning out trees around your yard to help alleviate the problem. Fertilize as recommended and try to manage harmful weeds that can deplete your soil’s nutrients.