Use a leather needle
If you’re making garments or small accessories you’ll likely be using a nice soft, lightweight leather. You shouldn’t need to buy special gadgets or equipment although I recommend using a special leather needle. It will help you get nice even stitches. However, a sharp new heavyweight needle (ie for upholstery or similar) will also do the trick).
Use household scissors, not your fabric shears
The simplest way to cut pattern pieces is to draw around them (you can use pretty much any pen, it won’t show through!) and cut using a rotary cutter or regular household or paper scissors. Make sure they’re nice and sharp (and clean!). Don’t use your fabric scissors to cut your leather as the leather will dull the blade really quickly.
Don’t use pins!
Step away from the pins! Using pins in leather will leave a hole. The good news is it tends not to slip about much so you should be ok without any pins. If you’re sewing up a long seam or just want to be extra careful you can always use a bit of double sided tape to keep the leather in the right place. Use it on the seam allowance only as you don’t want to gum up your needle.
Use a strong thread, polyester or nylon is best. Depending on what it is you’re making, some of the seams may be under a lot of pressure and you don’t want cotton threads deteriorating in time. Using a slightly longer stitch than usual will help strengthen the seams a bit as the holes will be further apart.
If you’re sewing with slightly bulkier leather or reach a point where you have many bulky seams converging you might find you need to use a walking foot on your machine (this is a special foot often used by quilters to feed several layers of fabric through at the same time). However, I have always used my regular presser foot when I’ve sewn leather and it’s been absolutely fine.
There’s no unpicking and sewing again! Once you’ve made a hole in the leather, either with a pin or stitching, it’s there forever! Take your time and practice on some scraps first.
Don’t use heat
You can’t iron leather! If you want seams to lay flat the best way is to finger press the seam open and then you can use something heavy to weight it down for a bit if you like. Top-stitching either side of your seams will keep them nice and flat, alternatively you could stick them down with tape.
Finishing your seams (or not!)
There’s no need to finish your seam edges (hurrah!) as leather won’t fray.