When choosing the name for your domain, always remember that:

• You can't use stressed vowels (such as à, é, ò, etc.)
• You can't use symbols (such as ' + . , | ! " £ $ % & / ( ) = ? ^ * ç ° § ; : _ > ] [ @ )
• The name's length must range between 3 and 63 characters (excluding the extension)
• The name can neither start nor end with the character "-", although the character "-" is allowed inside the name. 

So, to name your domain you can use any letter, numbers between 0 and 9, and the symbol "-". Length may vary, from 3 to 63 types. For domain names registered under the geographical structure, the limit is between 1 and 63 types.