It is fairly windy and still a bit chilly at night so this is what I do for the tomatoes and Brussels sprouts:
I set out my cages first and make sure they are evenly spaced, then I dig out a hole twice as deep as I want. I add a trowel of old bunny poop to the hole and mix it into the dirt a bit. Don't add fresh manure or it will burn your plant's roots. You could use well-rotted manure or compost. (I have rabbits so I use what I have on hand.)
Lastly I make a shallow trench around the bottom of the plastic and bury it slightly just so that the wind can't blow it around too much.
Later on in the season I will remove the plastic and mulch right to the base of the plants.