Whether faced with a lawn where you imagine a sea of flowers, or accepting the reality of poor soil, you can still have the garden of your dreams in a few easy steps:
Start saving up cardboard and newspapers;
Order soil for the new bed. Get the best organic mix (when in doubt, ask) and make sure you have enough for your raised bed. All of mine are 6 to 8 inches deep to provide proper rooting as well as good drainage;
Grab your garden hose (or rope). Do you want lots of room for plants or are you thinking of something akin to a necklace of plants surrounding your lawn? Either way, grab the hose (rope) and start laying out the bed. Keep in mind that plants get bigger over time, but don't go overboard and bite off more than you can chew. You can always bump out a bed if you want to make it bigger, but a large bed with only a few plants will look underwhelming. You also don't want to run out of steam in the middle of the project and abondon it.
Once you like the shape of the new bed, grab that stack of newspapers or cardboard and lay it on top of the grass. Use three to four sheets of newspaper for each section and lay them down with their edges overlapping. One layer of cardboard is enough; there is no need to double-up. It helps to do this on a windstill day; otherwise you will be chasing newspaper with every gust of wind. Wetting down the newspaper after you lay it down will help a little, but not a lot. It is also easier to work in small sections; lay down some paper or cardboard and then add the soil on top. Go on to the next section, and so on. Pretty soon you will have a nice empty bed where once there was lawn. And what about the grass underneath? Well, the paper or carbboard will smother the grass. I have noticed that worms (great gardeners' helpers!) have a tendency to congregate under the paper or cardboard because it stay just a bit more moist underneath.
As the grass dies, it will disintegrate and add to the nutrients in the soil. The worms will tunnel and move bits around, improving drainage as well as the condition of the soil. Meanwhile, with the good soil on top, your plants will be off to a great start. Again, keep in mind that these plants will grow bigger over time and although a PROPERLY planted garden will look a bit sparse the first year, it will make for happier, healthier plants down the road. You can always add annuals in between your perennials or shrubs that first year as the annuals will fill in while the perennials are catching up. An remember this old adage about perennial plants; the first year they sleep, the second year they creep and the third year they leap! So, keep in mind the mature size of the perennials and space them accordingly.
If at all possible (northern half of the country) add spring blooming bulbs in between your perennials for a great spring show. Daffodils will naturalize over time (increase in amounts), while most tulips usually peter out after a couple of years. Once your planting is done, you really should add a generous layer of mulch on top. This will shade the roots of your plants, keeping them cooler in the summer's heat while preserving moisture in the soil. A four inch layer of mulch is a generous amount. Today you can find some really great composted mulch which will add nutrients to your garden as it breaks down. Meanwhile those worms underground are working hard and will also help in improving your heavy clay soil or your sandy soil into something closer to a loamy soil. This process does not happen overnight, but in time you will improve your soil.
With your raised beds in place and planted make sure your water your plants on a regular basis as they establish themselves. Then, sit back and relax. Watching your garden grow is the enjoyable part of gardening. It is a journey to be enjoyed.