All winter long you've been itching to get out into your new garden. Well, you still have some waiting to do. Walking about on soil that is still cold and wet from the winter will cause an awful lot of damage. The first bit of harm will be the compaction of the saturated soil as it is compressed like a sponge. While the sponge will spring back, the soil will not. As the moisture is squeezed out the particles are mashed together preventing air entry. 
If you remember, the components of a good soil are sand, clay, humus and air. Secondly, damage will occur to the perennials that are still below the soil surface. The growing tips are quite tender and even the daintiest size fives will mash 'em real bad. Naturally, they will recover but their emergence will be delayed and you will have started them off under unwanted stress. At this time of the year, they have limited root reserves and no means of replenishing them. 
A good rule of thumb for knowing when to get busy gardening is to wait until the soil doesn't stick to your footwear. This is a good indication that excess moisture has drained away.
Now we can start our new plot. Use a hard backed rake and level out the soil that you tilled last fall, breaking up any remaining clods. You can make minor alterations in the drainage patterns now. Once you've done this preliminary cultivation, leave the plot alone. Let the soil warm up enough to germinate weeds left over from last year. After sprouting, you can give the bed another good raking. This can be an indicator of when to start plopping in perennials. An absolutely terrific book by Ray Lancaster, "What Perennial Where", will be a help. The local nurseries will have their early spring stock ready to go. Some plants can be placed into their new homes earlier than others but, again, don't rush. Let nature dictate the timing- this is an essential element to becoming a gardener. Mother Nature doesn't look at a calendar. Waiting for the May two-four weekend may be something that we do but it has little meaning to her, spring 1998 being a good example. 
Add some soil amendments if necessary- but only if necessary. A new piece of garden, unless something specific is missing, usually has decent soil, good structure ( because you tilled it properly) and an ample supply of nutrients. It may become apparent during the growing season that some elements are deficient. Top dressings of mulches, composts, or either slow-release or soluble fertilisers can be applied as remedies. 
Now comes the most difficult part of all and it has nothing at all to do with physical work. You must be true to your plan. You invested much time, mostly enjoyable I hope, developing your own rare design. Changes may be necessary when you visit the nursery and learn that a preferred variety is no longer available. Show your design to the friendly professional along with the particulars of the environment. Tell her the effect you would have liked the now unavailable plant to provide. She can suggest another that will fill the bill. In some nurseries, you may even be able to place an order for a specific specimen. 
Here is one last reminder. If your bed includes perennials, you may be dismayed to see how little space they cover. Huge barren expanses will seem to be the new theme of your plot. They will cover this area within three to five years. Meanwhile, you can plant annuals, ground covers, or use a decorative mulch.
I would really like to tell you that you can now sit back, relax and enjoy your new garden. Gentle readers, gardens are works in progress and are never ever completed. Isn't that nice?