The most important thing about saddle stitching is to be consistent and to always start a stitch from the same side, i.e. first left, then right or vice versa but never mixing. To saddle stitch, take the needle in your left hand and insert it through a hole to come out on the right. You should now have a needle in each hand. It is important to make sure you have an equal amount of thread on either side of the item. When you saddle stitch, you usually stitch toward yourself, however some prefer to stitch away from themselves, so choose what works for you.
Place the needle in your left hand through the next hole but do not pull the whole thread through yet, instead leave a small loop on the left. Take the needle in your right hand and push it through the same hole to come out on the left side. Before pulling this needle out of the hole, give the thread that is on the left a slight pull or tug to make sure that you have not pierced through it with your right needle. Then, pull both needles in opposite directions and pull the thread quite snug. When you are saddle stitching, always tighten with the same amount of strength to ensure an even-looking stitch line. Continue on to the next hole, first going in with the left needle, then the right and giving the thread a tug before tightening in opposite directions.
Some issues you might encounter when saddle stitching
You can’t pull the needle through the hole - Sometimes if the leather is really thick or the glue has dried up or your holes just aren’t lining up properly, it will be harder to get the needle to go through a hole. To fix this, you can make the hole a little bigger using your awl. If it’s the second needle that isn’t going through, use your awl to open up the hole but avoid piercing through the thread that is already in the hole. Try to pull the thread to one side of the hole and then gently push the awl in. You can also use pliers to pull your needles out if you can’t get a good grip. This might be especially helpful when back-stitching as there are so many layers of thread in one hole.
You pierce through the thread with your needle that is already in the hole - Go back through the same hole where you came in, with the same needle. You can usually clearly see where it pierced the thread and you can undo the knot. If you absolutely cannot undo it, you can cut your thread, melt down the ends of the thread with your lighter so that it does not unravel and then take a new piece of thread and continue where you left off.
The saddle stitching looks uneven and isn’t slanted like it’s supposed to - This is usually caused by not being consistent with how you saddle stitch. You should always start with the left needle, followed by the right (or the other way round if that is your preference - just be consistent). It takes practice to get a perfect stitch line when using the saddle stitch method so do not worry when you’re starting out. It takes practice.