I did similar things to help guide myself:

• Placing my pen down on the paper and using it to help visualize the line first, then I pick the pen back up and use what I learned from the visualization to help guide my lines

• Placing multiple dots, each time trying to better approximate the correct convergence for the line

• "Placing" the vanishing point using my eyes at some object which might be near or far. Like at an object on my desk, or maybe the wall, or even beyond wall in the next room or in the next building, etc. Just as a way to think about how near or far and in which direction the vanishing points were.

But at the end I simply dumped all the above techniques and just freehanded everything without stopping to think so much about every single detail. Once you get the understanding, potentially using techniques such as the above, you just do and let your intuition guide you.