Most backyards will have some areas of their lawn where the sun rarely shines upon. Try to trim back natural obstructions such as trees or tall plants to give your lawn more sunlight in these darker areas.
You may find it easier to create your lawn around where the sun shines to ensure a consistent lawn throughout. Grass needs sunlight to grow, but too much can also cause it to yellow and dry out.
Remember to give areas that get a lot of sunlight more water to stop your grass from changing colour.
You could look at adding trees or plants that can offer these dry areas more shade to reduce the impact of too much light during the dry seasons.
When looking at how to fertilise your lawn, more is not necessarily better. The signs of an over-fertilised lawn, commonly referred to as "fertiliser burn," results in dry brown stripes throughout the grass. The cause of the brown stripes is due to a build-up of salts within the soil, which dehydrates the grass, causing it to die off.
Although lawns do need to be fertilised, you should only need to do this once or perhaps twice per year. Never add fertiliser to a wet lawn, add it when dry, and then water it after to help let the goodness seep down to the roots where it will be most effective.
If your lawn does start to show signs of over-fertilisation, you should try watering it as much as possible to dilute the salts in the soil, and hopefully, they will drain away over time.