Rake back the mulch.  I'm assuming you're working with a no-till garden, mulched heavily for the winter to keep weeds from taking over.  (If not, you're going to have trouble planting early in the spring since your ground will probably be too wet to till, sometimes until June.)  While mulch is extremely handy during most of the year, the coating of organic matter acts like a layer of insulation in early spring, preventing the lengthening days from warming the ground.  The solution is simple --- rake back the mulch.  I usually pull my spring mulch to the sides of the beds a week or two before planting each one.  That way, weeds don't have time to grow, but the soil gets a chance to warm up.  Once the seedlings are a few inches tall, you can push the same mulch back up around their ankles, preventing competitive weeds from outgrowing your vegetables.

Add dark organic matter.  You've probably noticed how wearing a black shirt in the sun heats your body up quickly.  You can put the same science to work in the garden by topdressing your beds with a layer of dark-colored organic matter.  Good compost, well-rotted manure, or even biochar can work.  For more extreme soil preheating, you can lay down a dark sheet of plastic on the soil, but be aware that this technique can kill soil microorganisms.

Erect a quick hoop.  The quick hoops you built in October are easy to move to a fresh plot of land to create mini-greenhouses on top of your spring beds.  Putting up a quick hoop a week or two before planting can warm the soil by several degrees.