"I'm going to be starting 3 different kinds of pansies froom seeds, and
I wanted to know if there are any tips anyone can share? I've never
really started many flowers from seed, especially bedding-type plants.
The packets say to start 12 weeks before planting out, so the timing is
about right. Should I pinch them back at some point?"

I tried it once a couple years ago. Pansies are slow to germinate and
slow to grow to transplant size, so 12 weeks is what it takes.

My seed pack said to germinate in darkness and to my surprise, they
did.

Pansies are cool weather plants. They get leggy in the heat. If you
sow now, you/ll have sets in early May. The weather in Z7 turns hot in
mid-June, so you won/t have them around very long.

Better to sow in late June for setting out in the fall.