From what I gleaned you only find out if you are force sensitive by a Force user coming out of the cloest and telling you that you have the potential to become one of them.
Well with the odds being so low. How do I know its not a scam? Someone doing it just to get somthing from me, whether to join their faction or getting me to work for them.
Hmm, interesting question. I mean, I've seen newbies joining factions that - in the past - had the name of a Force using group, thinking that it would improve their chances of being Force Sensitive. However to my knowledge most - if not all - of those people did eventually get tested, and there were Force Users in those factions.
If you are in doubt, try asking one or more veteran players - usually they can be found on IRC (yes, I saw your other post asking about it. It really is recommended to get the most out of interactions in this game) and will know of a few Force Users. So if you ask around, you should get an idea of whether Joe Schmo is really Force Sensitive or not.
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"May the Grace of Ara go with you, and His Vengeance be wrought upon your enemies."