Carla from Virginia has this to add:
If you have only a short end remaining, first, DO NOT stitch too far.  It's better to start a new strand than to have to loop and attach threads. But you still have a short end, you say. On the back of your work: remove the needle from the thread. Push the needle through stitches on the back as though it were threaded, but not all the way through. The eye must be left open. Thread your short end into the needle (one of those threaders that are thin metal instead of wire helps
here). Pull the needle through the stitches you left it in. Note:  another reason not to use the shortest ends for stitching is they may lose their gloss or look fuzzy.

Carla also adds this:
1)  When stitching from a chart that you're working in sections for ease of stitching: 1) When stitching a large area of one color in sections, you DO NOT want to leave a straight vertical line of stitches inside the color area. The threads in the last stitches will all twist differently than the rest of the stitching. To avoid this, offset every other row by one stitch. Your stitches will look like this:
XXXX
XXX
XXXX.
Lightly shade in with a pencil on the chart the sections as you do them
2)  I have found that 2 strands of floss rarely cover 14 count adequately. I either use 3 strands or use 16 count fabric. Using 16 count will not adversely affect the size of the piece.
3) When cross-stitching over one on linen or other evenweave fabric, complete both legs of each cross stitch before moving on. The stitches will not slip under the weave if you do this.
4) When using over-dyes or variegated floss, completing each cross-stitch will make the colors seem to flow just like on the floss. This is very important when then colors are very different, like in a blend of fiesta colors.

Buy a microwave oven.  You can stitch longer and spend less time cooking.

Never go anywhere without some stitching.  Even waiting in the doctor or dentist office isn't bad if you are working on your own project.  Remember to take individual packets of moist towelettes to clean your hands before stitching.

Never use hand lotion before starting to work.  Oil from your hands is bad enough - lotion adds to the problem.

Generally work the design from top to bottom.

Keep even tension on your fabric and consistent tension on your stitches.

Cross all stitches in the same direction.

Work individual stitches from bottom to top.

On vertical rows, cross your stitches as you go.

Drop your needle occasionally to untwist the floss.

Baste guidelines on fabric to be stitched on.  It helps immeasurably to keep track of where you are.

It's difficult to follow a chart when you are at a meeting or visiting with friends.  At home, do the cross stitches all around the edges of areas, then just fill them in while you are visiting.

When doing borders, it will save much time and frustration if you start the top border in the middle and work to the edge.  Do the side border next.  Work from the center to the top edge.  Any need for compensation can then be done at the corners.

If you dislike background, do it as you work your piece.

It is very helpful sometimes to turn your work upside down (180 degrees), turning the chart as well but never turn the work only halfway around (90 degrees).  This causes the direction of the top stitch to change, disrupting the texture of the finished piece.

If you're working on a geometric design, backstitch an upward pointing arrow in the upper left corner of your work - and you'll always know which way is "up".

When you over-zealously stitch away until there is an impossibly short tail remaining - there is an easy remedy.  Remove the needle from the working thread.  Thread the needle with the ends of a doubled strand of scrap thread, forming a loop.  Continue the stitch with the needle and scrap thread.  Before the loop is drawn into the stitched fabric, catch the short working thread in the loop and complete the stitch.

Have a black cloth ready to put on your lap when wearing light colored clothing and stitching on light colored canvas or perforated paper.  The holes will stand out better.

Insert projects not being worked on in a pillowcase.  Then clip the pillowcase onto a skirt or pants hanger and hang in the closet.  This solves a storage problem for those larger pieces that may be on stretcher bars.

Many left handers have a problem with their threads (especially Perle Cotton) losing their twist. This is because most embroidery thread is designed for right handers. To keep this from happening left handers need to deliberately twist your needle in the direction of the thread twist. Do this every few stitched, and it will help keep the twist in the thread.

Thread has "nap". Examine the thread by holding it up to a good light before threading your needle. If you run part of the thread between two fingers - first one direction and then the other direction you can see how the little fibers lay. Thread your needle so that the thread fibers will lay down when pulling through the fabric. You will have a much neater looking surface if you do this.