I know this is a little early, but it's good to be prepared. In a couple weeks it will be time to plant your crowns (the root ball). Whatever you plant this year won't be able to be harvested, but in two years, however, you will be rewarded in early spring with a bonanza of tasty shoots. It's a longer-term investment in the beginning, but the plants are perennial and will live for 15-20 years.
One of the objections I've seen to planting asparagus is that it takes up too much room for a crop that only pops up in the early spring. The remedy to that is to interplant it with strawberries. They both have the same soil needs, and the asparagus won't interfere with the strawberries much, and vice versa. Problem solved.
Asparagus is an interesting plant in that it is either male or female. The technical term for that is dioecious. The male stalks are more productive and live longer, so if you are planting heirloom plants you'll need more than if you get a hybridized all-male variety, or weed out the female plants and put in more males in another year. If you have a smaller space to grow in it might be better in this instance to get a hybrid. One of the very few times I'll say that, actually...
How to plant it
Keep in mind that asparagus prefers full sun, but will tolerate a bit of shade, and they need a lighter, well-drained soil that warms up quickly in the spring. Since any standing water will rot the roots, raised beds are a perfect environment for them. The bed should be dug over with plenty of compost and manure to give the plants a good start.
