There are a lot of things you can do to make your garden more appealing and
safer for visiting hedgehogs -- all of which will encourage them to visit.
Of course, having a bumper crop of slugs and beetles is probably number one
on the hedgehog's list, but likely somewhere below the bottom of yours!

If you want to attract hedgehogs to your garden (assuming they are native to
your area), one of the best ways (as always with hedgehogs) is bribery.  Put
out some food, preferably something like canned cat or dog food, or some
cooked eggs (scrambled supposedly works well).

Fresh water is always a good lure too, though beware of offering too much in
the way of a swimming pool without a way out (see section [12.7]).

One thing to beware of is that most pesticides are not safe for hedgehogs.
If you use a lot of pesticides on your garden, you should not be trying to
attract hedgehogs, unless the idea is to replace the pesticides with the
hedgehogs, and if so, discontinue the pesticides first.

Probably the biggest worry in this respect (pesticides) is slug bait.  If
there are hedgehogs in your area, you should not be using slug bait as it
will almost certainly find its way into a hedgehog with unpleasant and often
dire consequences for the hedgehog.  There are plenty of safe ways to deal
with slugs -- including hedgehogs.