Speak clearly, use professional language and enunciate well so you are easily understood.
Avoid using 'cheers', 'uh-huh', 'mate', 'yeah', 'um' etc. Keep it friendly but business-like; you are speaking to a business contact not your drinking buddy. Learning the phonetic alphabet and using it to confirm spellings can help to keep a level of professionalism. E for Echo sounds much better than 'That's E for Eccentric?'
Stay tuned for more phone communication tips from Intercon Messaging!