You have a number of options.
If you don't know or trust each other, you can have the money held in escrow to protect both parties. There's obviously a cost for this service.
Otherwise, they could transfer the money to you and then you transfer the domain over. That way they have to trust you - but they at least have an idea of who you are. Depends how much the domain's worth obviously.
If i use an escrow then i may aswell use Sedo.
He has offered £750, not a great deal but an amount im happy to sell for.
Say he Paypal, Moneybooker me the money, then i transfer the domain, can they then dispute easily and get there money back?
Any ideas on the safety of the money transfer would be much apprecitaed.
Also worth noting, this isnt a person i know and have just had contact via email so far.
Cheers