For times, just about any tri will have last years results to gauge were you are going to end up. That said conditions change year to year, bike times alone were down over 5 minutes at the lats tri I did year over year becuase the weather was horrible last year.
My strategy:
The first tri, don't drown, don't end up last.
The first year, do my best and gauge were I ended up.
The next year, better my times for the same tri year over year.
Now, I try to improve my placing amongst my group (clydes)
Becuase every course is different, its really difficult to compare tri against tri for times. Also, the number and level of competitors is different depending on the tri.
Just have fun the first one, thats the great thing about tris.