Two techniques borrowed from embroidery but widely used in cross-stitch are back-stitch and French knots. These are two great methods of adding detail and texture to your piece. If your charts asks you to use back-stitch or French knots in the design, don’t be alarmed- they are both simple to learn and easy to do. 

Back-stitch

Back-stitch is usually worked in either one or two strands of thread (your chart which tell you how many strands you need to use) and involves making lots of little straight stitches which join up to form larger lines. Usually we work backwards- hence the name-, bring the thread up at the point when we want the stitch to end and then working back to meet the end of the last stitch. Although there is no hard and fast rule as to how long is too long for individual back-stitches, I usually keep my individual stitches around the same length as one leg of a cross-stitch. Just follow the lines on your chart closely to make sure you are placing your back-stitches in the correct place. 

French Knots

Although French knots are LOATHED by some stitchers, they aren’t as bad as some might have you believe.
To work a French knot, bring needle up at the point where you want the stitch to be, wrap your thread twice around the needle- making sure to keep a little tension on it- then point your needle back down towards the fabric and insert the needle at a point very close to where you brought it up. Don’t put the needle back down through the exact hole you came up through as you risk pulling the French knot through to the back of your fabric. 
Hint: if you really don’t like making French knots, you can use a bead instead.