How do I determine when to water my tomatoes in a pot?

I have 2 plants each in a big pot:(one per pot)
one is a patio hybrid cherry tomato
other is a Ramapo

I've done both before, in pots, great results - but I do not recall how I decided when to water them.
I watered thoroughly when I planted them one week ago. I mulched.
yesterday when I went to garden and felt the surface, it was moist, so I didn't water.

The soil is a combination of store-bought potting soil - Fafard - good stuff,  my own compost - a lot, and some store-bought compost.

I used to grow them in driveway, against a brick building, sheltered area.

Now they are in my garden, full sun, open area - more wind.
Most things dry out faster here, and the temp is usually cooler than in the city.

As for the size of the pot, that probably makes a difference, I'll measure when I go to garden. For now, I would estimate about 24 inches across and 24 down, and they are plastic.

And, I assume I should water til the water comes out the bottom?

Thanks for any ideas.