I'm sure this has been asked before, but I've not had much success in finding an answer and I don't have the book yet, so I'll ask anyway. When you select one of the Form technique talents, do you always have to use that Characteristic or is it only with talents?

For example, when you make a regular attack roll, does it use the alternate Characteristic or can you still use Brawn?

When you take one of the Form Technique talents, you have the option of using Brawn or the alternative characteristic, at least when you're making regular Lightsaber checks. Which can be helpful if you suffer a critical injury that impacts your alternate characteristic (such as suffering increased difficulties on any Cunning checks when you've got the Shien Technique talent), enabling you to default back to Brawn to avoid the extra difficulty die on your attacks.

The only time you have to use the characteristic listed with a Form Technique talent is for that Form's unique talents, such as Hawk-Bat Swoop and Saber Swarm only working with Lightsaber (Agility) checks as called out in those two talents. With the exception of Shii-Cho Knight, all of the LS Form specializations have high-level talents that require you to also have the Form Technique talent of that spec; if you can't make a LIghtsaber (Intellect) check because you danced around Soresu Technique, then you can't use the Defensive Circle talent.

Awesome, thanks!

DM is right on the money in this case, and this response is just to embellish on his response in hopes of provide some insight on the "Why" when referencing other rules, because this kind of stuff comes up a lot. The language of the options in these talents is very subtle. For example, the Ataru Striker talent is worded:

"When making a Lightsaber skill check, the character may use Agility instead of Brawn." [Emphasis mine]

The only word that clarifies that there's an option is "may", which is permissive, as compared to alternate wording, e.g. "must." So... yeah, subtle. This also solves the 'problem' (that doesn't actually exist) as to what to do if a character has two style talents, and provides a mechanical reason why there's no Shii-Cho form talent.

In contrast, the abilities like Saber Swarm work very differently, and explicitly state the Skill/Characteristic pairing that activates the talent. I mainly bring this up because it goes to show how incredibly important it is to read the full descriptions of talents, not just the text in the pretty little boxes on the trees. Lots of important details are hiding in that fine print.