If you are thinking of growing your own Asparagus you should begin by preparing the site now, weed thoroughly removing all perennial weeds and roots and incorporating plenty of Organic Matter ready for planting in a few weeks time.
Asparagus beds are a long term investment and not part of crop rotation, so you will need a sunny area that can be set aside as a permanent site.
A well managed bed can continue to crop for well over 20 years, so good initial preparation will pay dividends for the future of your crop. In future seasons keep weeds at bay and top dress every spring.
Having made such a thorough job of preparing your bed, make sure you buy only first quality one year old Asparagus Crowns. Plant them 12-18in apart (a double staggered row 18in apart will maximise your space).
Do not harvest in the first year, but allow the crowns to grow and develop a good root system, cut sparingly in the second year and by the third year you will have the best asparagus you have ever tasted!
(Rather than the insipid, imported spears to be found year round in supermarkets - which have all the flavour of damp cardboard!)