how to succesfully register a .it domain

If your business takes place even only partially in Italy, for you it's imperative to have your own .it domain.

For the recording of specific ccTLD, such as .it, it's not advisable to turn to big registrars like Godaddy or Tucows.
Aside from not being cost-effective, often they do not provide the specific expertise required.
I therefore advise you to contact a specific registrar, specialized in .it domains

Here you have the primary italian registrars, and their conditions:

Aruba

The largest registrar and hoster Italian, has its own webfarm Arezzo.
The price for a .it domain. (registration, renewal or transfer) is  9.99 €
Redemption price is not reported.
Their web-site is in italian only.

DomainRegister.it

Primary company, mainly specialized in the registration of domains of (more or less) every TLD, offering a more complete and professional service, also combined with an extremely affordable price.
The price for a .it domain. (registration, renewal or transfer) is 7,00 €
Redemption price is 14,00 €
Their web-site is both in italian and english.

Notes

For the registration of a .it domain, it's required the registrar be resident in Italy, or at least in an EU country.
If your company has a branch or a representative office in Italy, enter its address for the domain registration.
Otherwise ... the controls are not very strict: use the address of a friend, or of a relative ... ;-)
(if you want to do things pretty well, some Registrars offer a trustee service or local presence.)