If they are crooked in any way, your weave in your material will be crooked also. Make sure that all pieces are cut according to directions and that all tissue pieces, when placed on the material, are running according to the pattern instructions. If you accidentally place a pattern on the material going the wrong way, with some material, you can wind up with a shine or shading that will look different from the rest of the cut pattern pieces when the garment is finished. Now that you have laid out all the pattern pieces, pin them to the material. After pinning, take pinking shears, which are scissors with big teeth, and cut the pattern along the solid black line all around the pieces until they are cut out.
Pinking shears keep the material edges from fraying when cut.
Now take the tracing wheel and colored tracing paper, folding the paper so that both colored siides are facing the material and place the paper between the two pieces of dress where the darts are. These should be under the unprinted sides of the pattern and material, not on top of the pattern. Now, take your tracing wheel and run it along the printed darts on the pattern piece. When you are finished, you should have colored lines on your fabric that have marked where the darts will be on your dress. When done, find any other important items you need to mark, such as where the buttons will be, if any.