Negotiations: usng the Negotiation trigger has two functions: first to prevent a civ talking to the listener and second to act as a trigger for some action each time someone tries to contact the listener.
In this case, your civs won't talk, but if you try to talk, it will trigger an action if you want.
Example:
@IF
Negotiation
talker=Acoma
listener=?
talkertype=HumanorComputer
listenertype=HumanorComputer
@THEN
JustOnce
Text
^Negotiations for Cho-ja Hive take place. Cho-ja Hive unit arrives to defend Acoman capital.
EndText
CreatUnit
unit=Cho-ja Hive
owner=Acoma
veteran=no
homecity=none
Count=1
locations
xx,xx,y
endlocations
@ENDIF
I've used this as a way of giving the human player the ability to get military aid from allies.
Example:
@IF
Negotiation
talker=North Vietnamese
listener=Soviets
talkertype=HumanorComputer
listenertype=HumanorComputer
@THEN
JustOnce
Text
^We have requested aid from the Soviets. They have sent weapons to fight
the capitalist pigs!

...At a modest price.
EndText
CreatUnit
unit=Viet Cong
owner=North Vietnamese
veteran=no
homecity=none
Count=50
locations
xx,xx,y
endlocations
@THEN
CHANGEMONEY
receiver=North Vietnamese
amount=-1000
@ENDIF
So in this example, you contact the Soviets civ when you need reinforcements quickly. You would wait until you really need them though since you can only do it once (use JustOnce otherwise the human will just keep contacting the Soviets in the same turn until he reaches the limit as his treasury can go no lower than 0).
It's also an interesting way of giving the AI some randomness. Use Negotiation to create a unit whenever the AI talks (usually happens whenever their units come into contact). It could result in hundreds of units being created or just a few, depending on how the game playes out.
Bribing: In ToT, you can also make individual unit-types unbribable instead of having to use Democracy as is the case in MGE.
I'm not sure but I think ToT also supports a unit bribe trigger (check the macro).
Note that there's also a lot to be done with techs and flags so be sure to exploit that.
(One thing I like to do to keep all the civs at generally the same level is to give all civs a tech the moment it is discovered.