We worked outside, using our deep freeze as a work counter. Jim filled the pots with organic seed-starting soil, which is a finer grade than regular potting soil.
I planted a seed into each pot, 1/4" deep.
The seeds are very tiny! Well, YOU know. You've eaten a tomato!
We planted a flat and a half of Manitoba tomatoes. We grew some of these last year and enjoyed both the flavor and the fact that we were eating tomatoes weeks earlier than other years. They're a bit smaller, which means more work at canning time, though.

We also planted some Black Yum Yums and Duprava tomatoes. No idea what to expect on either of these!
Then we set this up on a table in front of the south window in our spare room. We put a long heating pad on low on the table, and straddled the three flats across the pad. Put water in the reservoirs, and covered with plastic. It will take a bit of time before we see what germinated.
Disclaimer: This is an experiment. We don't necessarily know what we're doing!