Pin 1 is the metal shell connection (internal shield), which should be grounded for proper shielding. On the 6SJ7GT glass version, pin 1 is the cathode connection only (no shell).
The 5693 is a ruggedised long-life variant (10,000+ hour rating) with identical electrical characteristics but tighter manufacturing tolerances.
12SJ7 is the 12.6V heater version (0.15A); electrically identical sections but not a drop-in substitute due to different heater requirements.
Triode connection is made by tying grids 2 and 3 to the anode. The RCA datasheet provides full triode-connected operating data at two plate voltage conditions.
The suppressor grid (g3) must be connected to cathode in pentode operation (internally connected on some variants, externally on pin 3 for the 6SJ7 metal type).
Heater-to-cathode voltage must not exceed 90V (either polarity). Keep heater-cathode potential difference as low as possible.