I like to have all communication done by e-mail/IM. I do not like to do business in this industry over the phone. I want a written record of what was communicated in case things go sideways. If there is a phone call, I would not let that be the final conversation, follow up with an e-mail detailing any important parts of the phone call. It's not just about fraud, there is to much chance for confusion in a transaction. Seen to many arguements here over what was communicated.
If an offer is totally unsolicited from an unknown party, I ask them to make their first offer also their final offer. I may say that I will only reply if the offer is accepted. Doesn't mean this is always the case, but if I'm looking for thousands and they are offering hundreds as their "final offer", I won't reply.