Even if you have put in most of your bedding plants (usually around Memorial Day), what Mr. C. has to say about transplanting may still benefit you this year or next - maybe for other vegetables, flowers, or volunteers*.
After I have planned my garden layout and prepared the soil (loostened beds with my favorite tool - a spading fork, and removed existing weeds), I take a trip to the Country Marketplace (my area greenhouse).
I barter some of the shallots** that I grew and dried last year in exchange for a discount on tomato and other plants. Having started my own plants in past years, I applaud them and those who also do their own plants. I choose healthy plants (not always the largest) that haven't outgrown the container (ie. gotten root-bound). I usually get 4 or 6 packs (if you want larger plants, consider individual plants).
I dig 6x6 inch holes, fill them half full with compost (you might use composted manure - available at Agway, etc) and mix it in.
Then I fill the holes with water, allow it to soak in, make a hole in the bottom with a hand trowel, put in a plant (to the depth of the first "true" leaves), and cover roots with the remaining soil.
I usually transplant in the evenings, so plants will have time to drink before the next days sun (the last picture below was taken a day after planting and shows no wilting). I put up tomato cages now (if I delay, I may wait too long) which I join together with twisters for mutual support. Now and as the plants grow and before the branches get too large, I pull them up over the support rings. Then I add a layer of compost over entire bed (to feed plants and retain moisture).
If and when watering is needed, early morning is the best time. This still gives time for absorption without promoting fungus that evening watering can cause.
Bonus tip: This hot weather can cause your spinach, basil (and other herbs) to start going to seed. Pluck them off to let plants continue to grow.
*Volunteers are any useful plant that re-seeds itself (ie. from last years gardening or in compost pile). If you can identify them, transplant as needed. Even small plants can produce in time.
**Shallots (bulbs of the onion family) multiply (like chives do) and can be used green, or if tops are allowed to die, can be dried, divided, and stored (in cool dry place) to be used in cooking or planting next year. For several years I have been growing them on the edges of my beds. They supposedly ward off insects and rabbits (a fence is more effective against rabbits).
