I recently asked this question also, but on my phone so can't find the link too easily!
The tips that helped me were to use "thread heaven", which is a thread conditioner and protectant (according to the label!). This helps the thread to glide a little easier.
Another tip was to rotate the needle a little after each stitch (in the opposite direction to the way it is twisted). This has helped me enormously!
I still get the occasional knot, but it's a lot more manageable now!