As part of our annual lawn care we scarify the lawns during September. There are various ways to achieve this depending on size of lawn and budget. The cheapest way is to vigorously hand rake the turf with a spring-tine rake. This method certainly works up a sweat but is the only practical solution for small areas. Another method is to attach a special blade, with springs at each end, to a rotary mower which converts it to a scarifier. For large areas hiring a specialist machine is the safest bet.
The reason behind scarifying is to remove the build up of ‘Thatch' and moss to allow air and light to the base and roots of the plants (people forget that a lawn is made up of lots of individual plants all of which need light, air, food and water).
Spiking or hollow-tining after will help alleviate any drainage/compaction issues. This is more noticeable on high wear areas which become well trodden.
Your lawn will look a lot worse before it gets better. But the effort will be worth it.