Purely from a character based rp advice, there's a few things that help out to set up.
Create a little bio for yourself
Name
Age
Goal(s)
Strengths
Flaws
Then a certain type or characteristic to base the character around: Highly inquisitive, relaxed, aggresive, aloof
This helps to build a bit of personality around.
Often the next step involves a hook or two, some little twists in the personality like 'very friendly, but when people ask about subject x, prone to turning passive aggresive'. Just a little thing that throws things around a bit, like the plot twist in a story.
And when you get that lined out, build a bit of a history story that incorperates these aspects.
Hope this helps, it's not a tight guideline but more a bit of a basic character rp setup!