This helps define your characters personality. A typical gesture. A typical mannerism. Expressions they like.
Ace: Physical quirks; Speaks in Imperial upper class accent most of the time. Have the mannerisms of a gentleman. Has piercing eyes. Mental quirks; Has strong emotions but shows little of them. Has lots of anger beneath the surface, but keeps it in strict control. Considers it a personal defeat if he gives in to the chaos within himself.
Do your character have any quirks?
The characters long terms goals. Examples; Personal power, gain wealth, finding your lost brother,
Ace: Restoring order in the galaxy. Become a Sith master. How does these goal combine? Ace wants to become more powerful, so he can gain respect and do more to achieve order in the galaxy. He wants peace and order despite being a Dark Jedi, because he admires efficiency and loathes chaos. This is his view of the Dark side, strict order to maximise efficiency, enforced if necessary.
Do your character have any goals?
This can be anything. Examples; Getting a better personal ship.
Ace: Is always on the lookout to acquire odd small arms, since this is his hobby.
Anything your character do on the side?
This is not necessarily fighting power, it can be many things. Examples; Remains cool under pressure. Is not afraid to accept help from others. Works easily in group. Is a natural leader.
Ace: Have a very disciplined mind, which helps him in almost any situation. However, this also leads him to be serious almost all the time, having little fun. He also adopts easily to new situations, and thus learn fast.
All characters have some strengths. Use them to your advantage.
Again, not necessarily about fighting abilities. Examples;
Ace: can loose control of his inner anger if injured or severely provoked, which could be disastrous - to him as well as people around him.
All characters have some weakness. Keep it in mind.
Does anyone have your characters loyalty or affection? Does other characters look up to your character? Is someone in love with you? If none, then can you develop relations over time?
Does anyone hate your character? Do your character hate anyone?
Do you have friends, or are you becoming friends with someone?
Your background should explain most of why your character is the one he/she is.
Why is he/she an Imperial/Dark Jedi/Spy/Pirate/Whatever?
Why does he/she hate Jedi/Rebels/Pirates/Whatever?
How come he/she is alien/bionic/nuts/whatever?
Why does he/she speak in a certain way?
How come he/she is rich/poor?
Ace: His accent comes from being brought up in an upper class family as an Imperial citizen. He never had much dealings with the Jedi, and doesn't hate them, he just feels contempt for the disorder they bring and their weakness, as he sees them. He comes from a very rich family and is used to having things done for him, but doesn't have access to the family fortune. He is used to all kinds of people as well as the criminal subculture from his time as a bounty hunter, where he also learned to be devious, keep the guard up, and many of his fighting skills.
How to write posts
How do you feel?
What are you thinking of?
Use your senses
What do you feel?
What do you see?
What do you hear?
What do you smell?
What do you taste?
What do you do?
What do others do?
What would you do in a given situation? Is it random, or predictable?
If someone prevents your action, do you have an alternative described or planned?
Is your action realistic? Could any Star Wars character do it? (Vader, Luke, Lando..) Could anyone do it?
Does your action makes sense? By the view of your character or others?
Do you have a plan on how to handle this situation, not just the present?
Keep your temper OOC. Remember, it's just a game.
Tell people when your are going to be away for a prolonged time.
I encourage you to state whenever you leave a current topic as well. You can always come back later, but don't leave threads hanging in nowhere left to die a slow death on their own. It's not only bad manners, the RPG suffers from it.
If in wonder, ask. But do it in the right place. A lot of OOC notes can ruin a going RPG.
If in doubt, do research. There's lots of information floating around on the internet. This makes your posts a lot more realistic, having a "Star Wars" feeling to it, and makes your posts a lot more worth reading.
Don't be afraid to edit if you see you wrote something wrong. We all do it at times, but we should strive to get it as good as we can.