That first one is not necessarily a killing frost. Even if it is, there are at least two simple ways to protect your plants: cover them with a sheet, blanket, or tablecloth; or turn your sprinklers on the garden overnight. That will form a layer of ice that protects the plants from dropping below 32 degrees. The plants won't die at the freezing point. How do you know if it will freeze at your house? The rule of thumb I use is: check the temperature outside at 10pm; it will drop about ten degrees more overnight.
So- if it's 42-44 degrees at 10pm, plan on protecting any plants you want to keep growing.
Things you can do in the garden right now, besides keeping up with the tomatoes and zucchini (!):
-trim asparagus plants to the ground
-put mulch around your rhubarb (it'll come up a little earlier that way)
and don't prune or fertilize bushes or trees right now; doing that now sends the plants a message to grow new branches. Those new ones will not be tough before winter, leading to extra winter damage.