It is a natural tendency for gardeners to order much more seed than they actually need. While you will want to plant your seeds thickly, you will eventually remove about half of the seeds that you plant to allow for adequate room, a process called “thinning”. So look over your list carefully and compare it to the space you have available. While you will be able to do some plantings a second time later on in a growing season (see: harvests and second plantings), you probably only need one bag of lettuce seeds. You also may not need more than one variety of any particular vegetable or fruit. Try one this year, and another next year.
Keep track of the seed varieties that interest you so you can remember them this time next year. The good news about seeds - they are very cheap!Mother Earth News: State-by-State Best Seed Company Compilation
Also, check out seed tips from the Farmers Almanac.
Next, see Preparing the Soil
