Loyalties
When lying, keep your actual loyalties as small in number as possible. Lying is all about serving yourself and perhaps your superiors and allies, if you have any. On the other hand, you should put across as honest and loyal a front as possible: be seen in the right company, donate to the right causes. The more trustworthy you seem, the more likely people are to trust you. The most skilled embezzlers have been with a company for years, diverting funds to their own accounts. Get in peoples' good books, but don't be fooled into thinking you owe them any sort of loyalty.
There is no truth.
You know, there are two kinds of truth. There's 'the truth' (frown, shakes head) and 'the truth' (smile, nods head vigorously)1. Perception is the name of the game.
Everyone does it.
Everyone lies! You know that. You're an average, regular kind of guy and you lie all the time. Therefore (ignoring everyone who insists on using logic here) everyone lies. No exceptions. If everyone does it, where's the harm? You're only lying to defend yourself from everyone else's lies. Anything you get by lying is legitimately yours. After all, the people you got the stuff from got it by lying too, right?
What Class?
The best liars are those with the highest Charisma scores and are able to take Bluff as a class skill. The best liars, therefore tend to be bards. Rogues are another good choice of class for this kind of work due to the number of skill points. The Bluff skill can be combined with the sneak attack to lethal effect.
A slightly unusual choice for a liar is the sorcerer. Sorcerers gained Bluff as a class skill when edition 3.5 was published, and all the best sorcerers have a high Charisma score. Give that a go too, see how it works. Don't bother if you're a paladin, however. Sure, you'll have the Charisma, but you're just not liar material. Sorry.
Skills
In the d20 system, the most important attribute to a negotiator is Charisma. If you can get the other person on your side, you've won half the battle. Not surprisingly, the key skills for a liar are Charisma-based.
- Bluff
- If there's one skill a liar needs above all others, it's Bluff. It grants you the ability to convince someone that things are other than they are for a short time. In short, the more ranks you have in Bluff, the more convincing you are. You can also use this skill to pass on secret messages to an accomplice -- very useful when trying to pluck a pigeon.
- Diplomacy
- What is lying, other than the art of negotiation? It's useful to keep as many people friendly as possible, and Diplomacy is absolutely invaluable when adjusting the attitudes of others: without it you're limited to making straight Charisma checks. Note that having 5 ranks in Bluff gives you a +2 synergy bonus to Diplomacy checks too. It pays to be a liar!
- Intimidate
- If you can't fool them, bully them. Intimidate can come in handy, and having 5 ranks in Bluff gets you a +2 synergy bonus to Intimidate skill checks. Of course, intimidation is an art all of its own, so we won't go into detail here.
- Sense Motive
- It is one thing to tell a lie, but any hardened liar suspects all others of being equally duplicitous. Make sure you can determine when other people are telling porky pies. Ignore this skill at your own risk! If said conman is trying to pass on a message to his assistant without you knowing, this skill lets you stay ahead of the game.