When I'm planting a new bed I like to set all my plants out before I start planting. I start by setting out my trees and shrubs. Then I place the plants that go around them and work outwards from there towards the edge of the bed. When you set the plants out first it gives you a chance to look over the layout before you get anything in the ground. Be sure to place the plants far enough apart to allow them to grow to their mature width without being crowded by their neighbor. This is also a good way to look at leaf texture since plants only bloom for a short part of the season it is good to have contrasting leaf textures and shades for year long visual appeal.
I like to put down mulch on the bed first before planting. When I plant I have to pull back the mulch and remove soil and then plant the plant and put the soil and mulch back without getting it all mixed together. An alternative is to plant the plants first and then cover each one with it's pot to protect it while you put down the mulch. Either way be careful to not cover the new plants over with mulch and to not have the mulch piled up against the stem of the plant.
After planting water everything really well. When placing the soil back air pockets are formed around the roots which can dry out the plant. When the plant is watered all the air pockets will fill up as the soil settles. When planting in hot weather you may see that the plants have wilted. Herbaceous plants can have some of their leaves removed to keep them from transpiring so much of their water and wilting. As the plants establish their roots they will also grow more leaves.
