Myth and Legend are full of tales of tricksters, cunning spirits and creatures that cause endless chaos in the lives of the heroes, always getting up to no good before - sometimes - getting caught up in their own deceitful webs. Depending on the games you run/play in, and the people you play with, it is probably only a matter of time before someone decides that they want to try playing a Trickster. However, I'm here to warn you that it may not play out as fun as it may seem at first.
Starting off, you're going to want to set this character up very similarly to the Gambler and the Mastermind that I talked about before. A lot of mental and social characteristics. You may also want to go and look at the Rogue write up while you are at it for some other advice on that. Most tricksters play into these three rolls, part gambler, part rogue, and part mastermind. Depending on the show/book/medium that you are taking inspiration for will shift which of those three any given Trickster will lean towards.
As Gamblers, Tricksters are usually cheats. Rigging the game with their tricks so that they come out ahead. As Masterminds, the Trickster rarely uses the orthodox move, instead relying on cunning and deception to deceive the enemy and strike where it is not expected - even if normally that would be the most expected place. Finally, as Rogues, Tricksters tend to be more light hearted and friendly. The kind of person who will steal your wallet just to see how long it will take you to notice it is missing, and to see what you'll do to get it back from that Bear's den.
PvP Is A Factor
So, one thing you need to be aware of if a player in your game is playing a Trickster, is that PvP will likely become a factor at some point. This could start as innocent fun, or it could be something a bit bigger than that. In my experience it is usually the innocent stuff. A light hearted prank of moving someone's stuff, taking a shiny bit of jewelery, or just rearranging a pack to make it hard to find things.
The problem with this comes when you have a player, or a PC, who just hates it when people screw with their stuff. Suddenly, that little prank has someone going nuts, and can very quickly escalate into a full out PVP engagement.
Even worse, some people just don't like being the victim of pranks, and Tricksters usually prey on those very people. As such, one person's fun can very quickly tread all over the others, causing an awkward situation for everyone around the table. Because of this, I caution you to pick who you allow to play a trickster carefully, and if your group doesn't have fun with it, then put a stop to it. Quickly.
Playing The Trickster
Enough about that don'ts, lets talk about the dos. So when you're playing the trickster you need to keep in mind the kind of trickster you are playing. If you are doing the more light hearted one, than keep it in mind. Keep the positive outlook going forward at all times, and use it to keep people off guard as you are moving around. In general, much like the mastermind and gambler, you need to be always watching. The best tricks are the ones that prey on the strengths and weaknesses of the people around you, and to do that you need to know those weaknesses.
Aside from that, know your marks and learn what you can about them before you do it. Plan your tricks well, start small, hit big, and fade. Make sure you always cover your tracks. Nothing is worse than being flagged as the trickster pulling the pranks. People don't often like that. To return briefly to PvP, try to play it light with the other players unless it is a PvP centric game. For one, they're not good game since they will see connections NPCs won't if only from simple genre savvy and being a player. For two, you don't want to ruin a friend's fun, do you?
I mentioned this above, but you need to stay innocent as a trickster. Now, play enough tricks and the people who know you are going to put two and two together, but that doesn't mean you want to just drop the veneer completely. Have alibis ready, have excuses, take care to be stealthy when you are up to no good. Keep moving, and don't forget the three Ds, Deny, Deny, and Deny. You don't even know what you know when pressed right.
Another fun way to do things if you don't know how to play innocent, is just go for crazy. You'll be amazed what people will believe if it sounds half-way sensical, when everything else that comes out of your mouth is complete non-sense. Claim to be King, Emperor, God, Hero. Claim to be owed money by people you meet. Claim whatever you can, the more outrageous the better. Be loud, be noticed, and be remembered. THen vanish briefly, have things go nuts, and reappear. No one that loud could have done that right? And when pressed, and pressed hard, and you give a somewhat sensible answer it'll probably even be believed.
Like with all character types you need to have fun with it. I recommend talking to your GM, but hell, I always recommend talking to the GM don't I? Find out from them how far you can go in their game. Talk to them abuot what you want to do, and how you want to go about it. You may also want to talk to the other players, and see who has issues OOC with being messed with. Leave those people alone, obviously.