Roger Doiron says that if ten percent of the lawn space in the US were converted to vegetable, fruit, herb and nectar plants, everyone in the country could have fresh local produce and by extension, perhaps, improved health.
Dioron's site, Kitchen Gardens International at http://kgi.org/ provides ongoing conversations and help that could make it possible if more potential gardeners could be recruited.
The Kitchen Gardening 101 tab under the Education drop down menu gives new gardeners enough information to get started. I wholeheartedly agree with the advice to start small and make a plan though I rarely plan anything myself.
If you'd like to hear Dioron, his TED talk is at http://kgi.org/education too. Definitely brows the Blog link http://kgi.org/blogs for dozens of useful articles.
The Deep Middle was all about converting lawn to garden this morning and is the source for my sending you to Kitchen Gardens International.
If you have a bit more browsing time and this topic interests you, click over to Edible Estates
and look at some of the lawn to garden conversions described and illustrated by Fritz Haeg. The scrolling photos at the top of each garden's page shows the progression.