Step one should always be to analyse your soil's structure and composition. For example, if you have a hard soil with little humus, like ours, your first goal would be to improve it's texture and health. Such a soil can be gradually improved by incorporating as much natural materials such as dried leaves, compost or manure. This process will take some take some time but over time you will see an improvement in your soils structure and health as your soil becomes richer in nutrients and minerals. As the soil improves it will provide plants with the means to resist disease and insect attack naturally.
Step two, should be to gradually incorporate the use of organic pest controls into your garden. You can make your own chemical free concoctions at home or alternatively there are now an endless array of commercial products available to deal with all your gardening problems.
Step three, should be your gradual move towards purchasing organic seeds. You will find a wide selection of these available from on-line seed sellers and most sites will indicate whether seeds are organic or not.
You can, over a period of your choice, become fully organic by following this four stage plan. Good luck and happy gardening.