The main thing that messed me up at first with lewis dot structures was thinking that a compound like SeCl4 would be a tetrahedral because of the number 4.
What I realized after making this chart, and memorizing it is that SeCl4 is actually a Trigonal Bipyramidal Seesaw! There are 5 regions, but only 4 bonds, therefore leaving 2 extra electrons. (Resembling AX4e)
I hope this chart helps you like it did me. I memorized it, and on my test day I wrote it out on a back of one of the test pages before I started my Lewis Structures.