Instead of issuing the 'Dock' command from several kilometres away you fly your ship to the docking ring and press F3 when you are immediately before the gap between the protector 'pincers'. This way you can dock without any delay whatsoever (the pincers won't even open).
Note: if you approach the docking ring frontally at cruise speed and you hit the wrong button then you will crash right into the planet. This can be very frustrating when you are a trader and all your money is in your cargo hold.
So it safer to come from the side but it is a bit trickier to hit the right spot at cruise speed. Try it at normal or even slower speed first until you know where the hot spot is.
Tradelane rings, jumpgates, jumpholes and docking bays work in a similar fashion except that you cannot dock sideways. I found it useful to bind the dock command to a more convenient key ('<') that can be found reliably without looking at the keyboard and without moving the left hand from the home position since the other fingers may have to operate afterburners, strafe keys or whatever at the same time.
If you do a bit of trading then perfecting your zero-delay docking skills is about the only thing you can do to relieve the boredom, except when you get jumped by pirates in which case that skill can save your butt.