Putting down a deposit.

You are right to consider safety when giving out your credit card. Many hotels and Trenitalia have systems for reservations where you have a better view of the process - and a printout of the results. PayPal is good too, for a fee. You get an immediate response from PayPal that the money arrived and is picked up. I use PayPal when renting an apartment. What I don't do is give the number out over the phone or by fax - I want a better sense of safety. I do remember several years ago the landlord requested the credit card number via email but said to send it in 2 or 3 sections. Guess that's supposed to deter hackers. I didn't stay there.

I used to send it by fax or two separate emails, but was convinced that neither is any safer than regular email. The chance of being hacked or intercepted are slim. The greatest risk is from someone at the receiving end ( unscrupulous employee?) copying it and passing it on. This is very unlikely in small family-run places.

You do know that if your card is scammed and used for unauthorized purchases, you are not responsible? You fraud department should catch it immediately. The hassle then is they send you a new card.

I have sent my credit card number and expiry date by email to B&Bs and small hotels in Europe several times with no problem, but of course that's just my experience. In the past I sent the information by fax, which I expect should be safer. But I think the risk by email is very low, frankly. If they want the security code on the back of the credit card as well, I would send that in a separate email message.

Best choice is paypal by far.

Safe and fees reasonable for the people getting it.
Bank transfer expensive for both parties.

I have sent it in two separate emails when required. But I make sure the hotels have good reviews on Trip Advisor or are Rick Steves approved first. I have not yet had problems.