Alright, so my post didn't go through or someone deleted it due to fair reasons.
If you are not able to give your character a story based on canon, and give it a nice touch how his/her life was before the event of the seven hour war.
You are not qualified to be a good roleplayer in Half-Life: Two Roleplay.
Simple as that,
-You need to know the canon, in order to make a good back-story.
-You must be able to quickly respond to something, not short answers or taking ages to respond to that something.
And, yes this must sound dumb.
-But you should be able to lie, if you are able to lie quickly and believable towards people in real-life. You are able to roleplay, this comes in place with quickly responding and the making up of stories.