Preventing Twists and Knots
Separate the floss into individual strands and then recombine them. This is known as "stripping" the floss. There is less twisting and knotting, and the stitches lie flatter. To separate a thread from the others, hold onto the top end of the thread between your thumb and forefinger. Pull down on it with the other thumb and forefinger, taking all the other threads with you. It looks like a knot will form. Have faith. Everything comes out just fine.
Run each separated strand of floss over a damp sponge just before using it. This makes the floss lie much smoother and flatter. Some fibres, such as silk, should not be dampened.
If you know which direction you tend to twist the needle, give it a little bit of a twist the opposite direction after each stitch.
Try threading the needle with the "right" end of the floss. See section "31.3 The Right End of the Floss" for more information.
Let the thread dangle every so often and untwist it.
Railroading
You can use a technique called railroading to prevent twisting. On the top half of the cross stitch, pull the needle and thread through to the front to start the stitch in the usual manner. Then put the tip of the needle between the two threads right where they come through the fabric so that the needle is pointing in the direction it needs to go to complete the stitch, and take it over to finish the stitch.
The dot in the diagram below represents where the needle is going to go to complete the stitch.
In case the directions above don't make sense, here is another description.
From: Martha Beth Lewis <marbeth@ix.netcom.com>...
Here is some lovely ascii art to get you started:
#
x
o
Bring the needle to the front of the work at o. You'll be going down at x, but don't do anything yet.
Take the thread coming out of o and lay it -on the surface- of the work. Put your finger at # on the two threads and hold them to the surface of the work. The threads should be lying from o to #, crossing x. Imagine they are two golf clubs lying parallel to each other on either side of the cup (the "cup" in this analogy is x).
Keeping your finger at #, put the needle in at x -between- the two threads. Lift your finger from #.
Now pull the thread all the way to the back. You will see that your two threads are lying perfectly parallel.
What railroading does is eliminate the twist in the thread, causing the stitch to lie beautifully bcs the two strands are completely parallel. The twist in the thread is actually transferred further up the tail of the thread, so you'll have to untwist a little more often than if you are not railroading your sts. By this I mean let the needle dangle from the underside of your work.
Railroading also makes the surface of the work flatter, improves floss coverage, and (some say) maximises light reflected by the floss.
Railroading adds time to each stitch. Those who stitch in competitions railroad all the time. Judges can tell the difference.
A short cut is to railroad only the half of the stitch that lies on top, as this is the one that is seen most clearly, although some stitchers say that they can see the bottom leg of the stitch clearly, too.
Try an experiment. Do a row or two of "unrailroaded" and some of "full railroaded." You'll see a definite difference. Now do a row of "half railroaded." What do you think? Is there enough of a difference to merit the extra time?
You get used to railroading and it becomes second nature, but it does add a lot of time to finishing the project. It's up to you whether you think the result is worth the extra time. As I mentioned above, judges seem to know the difference!
Laying Tools
A laying tool can help keep threads untwisted when you stitch with multiple strands of floss and other fibres. Using it requires an extra hand, so having the needlework in a frame on a stand helps.
Many things can be used as laying tools--a very large tapestry needle, a very small knitting needle, a trolley needle, or even a real laying tool.
Start your stitch by pulling the needle and thread through to the front as usual. Lightly pull the thread away from the direction of the stitch. Use the laying tool to stroke the thread against the fabric near where the thread emerges from the fabric. This should make the strands lie flat and parallel. Complete this part of the stitch by putting the needle into the fabric and pulling it to the back as usual. As you pull the thread through to the back, use the laying tool to keep a small amount of tension in the thread. This will keep those newly stroked strands parallel.