Whether you decide to grow from seed or purchase from a garden shop, moving seedlings into the ground is a necessary step. Some seeds are started in biodegradable containers which can be planted directly into the ground, but you'll need to ensure that the plant roots can easily push through to the garden soil.
The most important thing to remember is to plant at the appropriate time:
Always moisten the soil before transplanting, just like when you thinned your seedlings.
Once you've chosen a spot and prepared your seedlings, you can begin digging. The depth of the hole will depend on the type of plant, but most can be inserted as deep as their first set of leaves.
Adding some compost in and around the hole will help.
Now make a space in the loosened soil that's as wide as the seedling's roots, scoop the seedling up and place it inside. Gently fill the soil back into the hole while constantly keeping the seedling upright. When the soil is filled in, firmly pack the soil down around the base of the plant, ensuring that the plant is properly supported.
The final step is to water liberally. The water will help settle the soil, increasing support for the plant and contact between the soil and roots.
If there is no rain in the forecast, you'll need to water daily until it recovers from the shock of being transplanted.