You can't I'm afraid - they are just the fruiting bodies of mycelium underground, which probably run right through the lawn. If you've got dead wood in the garden, such as old tree stumps, they may be present in association with that,so having that removed should reduce the population over time, but this seems to be a very good year for toadstools and mushrooms in the UK, they're everywhere. They'll disappear on their own after a week or two, but if you don't like the look of them,twist them off wearing gloves and dispose of them.

This is part of nature's composting process and is a very good indication for your soil.

Increasing the diversity of the soil organisms in the lawn will help reduce the toadstools, too. Applying a thin layer of a good, rich compost twice a year will help with this, or applying a good, two-day compost tea.

Tug, how does it do that?

Frankly, I don't think they're worth the bother. They're here today, gone tomorrow.They won't hurt anything. They seem to pop up mostly in Autumn.

A few species are poisonous if eaten so if there are children around make sure they are taught - or better still if concerned ask the local fungus group to identify them for you. But brushing them off as they appear is simpler.

It's true some species of mushrooms are poisonous if eaten, and many plants are as well. However, I can't recall of a single case of somebody actually being poisoned but of course you can't be too cautious.

Stera, it increases the amount of "edible" organic matter in the soil, which will provide more ecological niches for different soil organisms. Each batch of compost or compost tea has a slightly different mix of microorganisms in it, so new ones are coming in almost with each application. Once there are more kinds fungi and bacteria competing for the organic matter, the toadstool fungi will have a smaller share of the crude dead matter, and there will be a gradual reduction in the toadstools above ground.

Goodness, it must take quite a long time to achieve that. But how would you do it? You can hardly put a thick layer of compost on the lawn... Thank you for the explanation.
There are some less common toadstools that will only grow on unimproved grassland - hygrophorus for instance.

Just as I said, thin layers of sifted compost, raked well in, or compost tea.

No chance of us doing that - uneven ratio of compost to lawn...Anyway I like toadstools a lot!

A lot of them are kind of pretty, especially the most poisonous ones. :)

Including the pretty fly agaric that grows under birch trees.
One year there was a huge crop of them in the little patch of woodland at the local college and the caretaker knocked them all down - someone must have let on that they are hallucinogenic. I bet the students thought him a spoilsport...
I have a pottery Destroying Angel on the piano along with a few others. It takes all sorts!