I usually hand pick my squadron and starting date. The main criteria for my choice of unit is usually that hey have interesting and varying selection of aircraft.
I originally started in Jasta 17 because it had nice progression in plane types from late 1916 onward (Including the early Fokker D-types). However they had me flying Fokker E.III even when I was the top scoring pilot of the unit and that ended up almost ending my career as I was badly beaten in a dogfight by Strutter.
After six weeks in French military hospital (and completely missing the brief period where Fokker D-types were in use) I sought transfer to Jasta 7. The main reasons were that they had Abatros D.Is and D.IIs and I liked the unit's color scheme (turns out it's not used before June 1917 though).
So far in this campaign I have finished 47 missions and I have flown Fokker E.III, Halberstadt D.II, Halberstadt D.III, Albatros D.I and Albatros D.II so far. I just requested transfer to newly formed Jasta 29 as they have early Albatros D.IIIs for middle and high ranks to fly and they are positioned in a part of the front I have not been to before.