Making sure you match the needles to the fabric is important here. Most fashion velvets are fairly lightweight so a Universal 70 – 80 needle will be fine. If working with velour (stretch velvet) make sure you are using ballpoint or stretch needles. Always use a new one for a new project.
Hand sewing needles need to be Sharps as well to make sure they won’t snag any threads in the back of the velvet.
You don’t need any special machinery to sew velvet but it is trickier to sew than normal fabric because of the ‘creep’ created by the pile. To minimise this you can use a walking foot to feed both layers of the fabric under the presser foot more evenly. But check on a scrap that it will not create indented marks on the velvet’s surface.
Hand tack/baste the seams together. Sewing with angled stitches will minimise the movement of the fabric. You could also sew back-stitch here too.
You can also try adding a layer of tissue paper between the layers of velvet before basting. This just prevents the pile rubbing next to itself and creating the fabric creep.
If all else fails you can just glue it. Using a temporary spray adhesive just along the seam line will allow you to stick the two layers together and then peel it off and reposition if necessary. The glue will just dissipate after a period of time leaving no residue on the fabric. I like to mask off an area to spray so it doesn’t go everywhere.
Remember to lengthen the stitch to cater for the pile and you may want to experiment with reducing the presser foot pressure too. If you are sewing velour on an overlocker you will need to adjust the differential feed to cater for the stretch in the fabric.
The answer to all the above is Test, Test, Test! Always test the settings on the machines you are using on scraps of fabric first. Record the settings on the machine when you are happy with the results as this will be a guide to refer to when you come to use a similar fabric again. Yes there will be a next time!