Don't let the soil dry out. Plants stored in a dark location like a basement or in the garage longer than a single night or day, can be damaged. For more info see Soil Smarts . Regardless of the condition of your soil it can never hurt to add extra organic material - compost, peat moss or manure to your garden each year at the beginning of the growing season. Mix in a little inorganic fertilizer as well.
Organic matter works like a sponge, improving the soil's ability to retain most nutrients and water.
Inorganic fertilizer completes the balance of nutrients a soil needs to be considered good soil. Good soil makes a good foundation for good plants. Make sure they have been acclimatized to the outdoor world for at least a week. This means hardening off the plant little by little from its' protected greenhouse environment allowing it to develop a hardiness to the elements of the great outdoors. If you don't harden them off, the shock of the climate change could kill them.