Which period are you interested in? During the Medieval period various insurances could be employed, such as exchanging hostages or issuing 'safe conducts'. If you mean more recently, there was a trend of convening meetings in neutral territories, such as Ronald Reagan and Mikhail Gorbachev choosing to meet in Reykjavik, rather than either of their own capitals. We also now have the Vienna Convention on diplomatic relations and long traditions of protocol.

What kind of era are you looking for information on?

Edit: Spelling.