Mowing will be the most frequent maintenance that your lawn needs. It is an important task as it ensures that the lawn remains healthy. However, it is not quite as straight forward as simply running the lawn mower over the grass every now and then.
A new lawn will normally be ready for its first mow around 10 days after it has been laid. Check to make sure the turf has rooted in first though. You can do this by lifting up a corner of the turf and seeing whether the roots have anchored down. This takes longer in colder weather than hot, and there is no exact timing. For the first mow, use the lawn mowers highest setting. There after, do not take more than a third of the length of the turf off during any cut.
In the spring you will need to mow around once a week. You may have to increase this in the summer, although be careful if it is particularly hot and dry. You should not have to mow the lawn in the winter as the turf stops growing at temperatures below 5 degrees.
Be careful not to mow the lawn too short. Close mowing weakens the grass and encourages shallow roots, making the lawn more prone to moss and weeds. You can even potentially scalp the lawn, leaving brown patches that will probably need a bit of work to restore. Scalping can also be caused by uneven ground, such as areas around tree roots.
Leaving the grass to grow too long can also cause issues. If this does happen, do not be tempted to cut it all back in one go, stick to the third off the blade rule. Other than it being quite difficult to do, mowing the lawn causes stress to the grass as it removes some of its ability to photosynthesise. So let it recover for a few days between cuts, until you have your desired height back.
Never leave the grass cuttings on the turf as they block the sunlight to lawn below, which cause it to die off. Grass cuttings make great compost, so why not put them on your compost heap and recycle them later in your garden.