Personality
This is something that you may find developing over time, and it can be one of the hardest things to just 'start' from nowhere. A good way to start a character personality is to define one or two general characteristics - 'bossy,' 'shy,' 'warm,' 'thoughtful,' - and work with these for a while until you find a niche. A warning: If you choose 'antagonistic' or 'loud' or 'rude' people will probably respond to those characteristics in a logical way - that is, not very nicely. Usually it's best to get to know the game and its players before attempting a character like this, as fun to play as they can be.
Looking to our new character, Colin, we can give him some personality from the start. The rest we will develop as we continue to play him. Characters tend to take on personalities of their own.
Since Colin is from a Hold, his upbringing is stricter than those raised in a Weyr. When approached by riders or unknown people, he will be shy. When it comes to his friends, he is friendly, open, and always in the middle of a conversation or ten.
Wasn't that painless? Of course it was. Now, Colin is ready to play. So go on! Go! Go! Get out there and RP!