Northern & Central Midwest
Avoid Damping Off
Avoid damping off by cleaning all flats and pots you use for starting seedlings. Wash in hot soapy water and then soak ten minute in a bleach solution of 10 parts water to 1 part bleach. Make sure to use clean, sterile potting mix to avoid fungal contamination.
If your soil dries out enough to rake lightly, you can plant your lettuce seeds. Sprinkle seeds on the soil and rake lightly. Even if the soil is moist, water in the seeds gently in order to get good contact with the soil. Make sure to keep them watered through the germination process.
Plant onion sets or plants as soon as the soil is dry enough to be worked. Onion sets will give you scallions for early spring, and plants will give you bulbing and storage onions. Water in well and have mulch ready to apply when the soil warms and summer is imminent.
Clean Up Flower Beds
Remove dead foliage and weeds in perennial and annual beds. You can pull back the mulch around crowns, but be ready to pull it back in case of an imminent hard freeze. Gently push any heaved plants back in the ground and firm the soil -- don't step on them to push them back into the soil.
Remove Iris Foliage
As soon as you can get into the garden, clear away all the mulch around iris and remove every shred of old foliage. This is where iris borer eggs reside, and clearing away the foliage and destroying the eggs will go a long way to reducing your borer populations.