If you have a mower that mulches as well as catches this helps to return nutrients back into the soil and to help the grass to retain moisture. Leaving the clippings on the lawn is also useful from time to time.
Thatch is the dead undecomposed matter from the grass and roots. If not removed thatch, will prevent entry of air, water and fertilizer in to the soil. Use a metal rake to rake the thatch out this is best done in early spring to give the grass room for new growth.
Aerating improves the lawns access to oxygen, helps new roots to penetrate the soil, allows in water and fertilizers. Aerating is particularly important for clay soil that compacts easily. You can use a pitch folk or use a coring machine for bigger areas. Coring machines have hollow plugs that leave long holes and core material. When dry use a rake to rake the core material back in to the lawn. Aerating is essential for getting no growth areas growing. After coring you can fertilize or add lime or dolomite if you soil has a low ph level.
Soil wetters can be very valuable in increasing the amount of water that penetrates the root zone. If you have hydrophobic soil, wetters can help a great deal.