Get a couple of manuals and start with the lowest starting load. I work up usually in about five increments from start to max.
Unique, as much as I like the powder, has not been very good in 9x19. The most accurate powder in my 9x19s has been Power Pistol (used to be Herco before PP came out and I got some). Other really good powders are Silhouette, True Blue, Herco (of course), N340, and AA5. Some have found WSF to be very good, but my pistols haven't cared for it.
Load a couple of inert dummy rounds at max COL, remove enough case mouth flare so rounds will chamber (or, if loading jacketed, try no flare at all), and work COL down until the rounds feed and chamber. I found that hand cycling carefully is best for Lugers (P-08s), as I don't have the same ability to pull the toggle as I do a slide. In general, the most accurate COL is the longest that feeds and chambers 100%.
COL depends on many things: the exact ogive geometry of the bullet, the magazine (how long a round it will hold and when it releases the round to be fed), the feed ramp, and the chamber (particularly the throat). Thus, COLs in manuals can be no more than a minimum the data applies to, since they don't have the exact same variables you have.
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