I'm in the same boat as you. This sans watering thing can get complicated. There's just so much information out there. My mother has the really common sans you see in stores all the time. It is in a glazed, six inch pot about a foot away from a south window. She says she waters hers about every 7 or 14 days. She doesn't keep track strictly. Just when it's dry. It's been growing like crazy over the past two years. I have some sans too. Four types. They have been doing pretty well for me all spring. I have decided to let the soil dry all the way through then wait a few more days, and then water. Right now they are in 3 - 4 inch pots. I have been watering probably every 9 or 10 days. That's only because they're growing right now though. When they go dormant, or stop growing for a time, I will wait until the leaves become slightly wilty or bendy.

Here in Houston, we're having record heat (up to 105 a few days ago) AND we're in the middle of a -18" drought (worst since 1956). I'm watering at first light and right after sundown during the week. On weekends when I'm home I'll give a mid-day watering, as well. Leaves are STILL brown and crunch and hardly any blooms are intact on my Nikko, Mdm Emilloire, Masjas, T&S, ES and Nantucket blue, which get a lot of sun and the last 3 are in pots. The ASB, Trophee and Oregon Pride which are in the ground and get less sun are doing fine (though all their blooms are white or nearly white... not sure what's up with that). So, depends on the situation. It's not possible to overwater them right now where I am.

Tomatoes require a minimum of 1" of water per week (1.5" in a sandy, fast-draining soil). You are right, deep watering is best. Tomatoes also need consistent soil moisture, as fluctuations can cause cracking and/or blossom end rot. A good layer of mulch will help maintain more consistent soil temperature and moisture levels, as well as help keep weeds down. Don't panic if you don't have a lot of tomatoes during this very hot weather. The plants often will not set fruit if temperatures are above 90 degrees. Rutgers Cooperative Extension has a few fact sheets on growing tomatoes in the home garden; a link for one of them is below. Here is a link that might be useful: Growing Tomatoes in the Home Garden

I don't have spider plants, but those who do pretty would want to know what kind of soil you use before giving you advice. That's because many folks around here use growing media made of large particles that drain very quickly and stay aerated even right after watering, which calls for very different watering habits than the more common fine grained peat based potting soil. Hopefully this bump will attract more attention.