It may help to ask them for further clarification of a claim, or to put the claim in writing. Another common type of tactic is psychological warfare. When the tricky party uses a stressful environment, the principled party should identify the problematic element and suggest a more comfortable or fair change. Subtle personal attacks can be made less effective simply be recognizing them for what they are. Explicitly identifying them to the offending party will often put an end to suck attacks.
Threats are a way to apply psychological pressure.
The principled negotiator should ignore them where possible, or undertake principled negotiations on the use of threats in the proceedings. The last class of trick tactics are positional pressure tactics which attempt to structure negotiations so that only one side can make concessions. The tricky side may refuse to negotiate, hoping to use their entry into negotiations as a bargaining chip, or they may open with extreme demands. The principled negotiator should recognize this as a bargaining tactic, and look into their interests in refusing to negotiate. They may escalate their demands for every concession they make.