At this point, I would like to underline the necessity of a multimeter. If possible, it should be equipped with an audible continuity checker. This tool is crucial when checking the integrity of our construct.

After all connections have been made, I just use my multimeter's beeping continuity checker, just to be on the safe side, especially for the power lines.

After all lines are verified, I connect everything except the LCD itself. While all power is running, I again use the multimeter to verify the voltages that reach each pin. The lines coming from the parallel port should be either +5V or 0V. That is normal. The power feed pin voltage should not exceed +5, the GND pin should be 0V (zero), and the rest of the pins should react according their function; for instance, if there is a RST (reset) pin, along with a reset momentary switch on my circuit board, the voltage of that pin should react to the pressing of the according button!

[NOTE] One thing that is not to be feared, is the multimeter. On voltage measuring setting, it is safe to be used on anything, even modern motherboards.
Of course, attention must be paid not to short-circuit anything with its probes!
If used correctly, it can easily prove to be the most useful piece of equipment!

The one thing that is of paramount importance, is: the LCD must remain alive. Even if all data and control lines are scrambled as hell, nothing will happen to the LCD. However, just half a second of, say, inverted power polarity, and the LCD is up in smoke (trust me, I know)! So, check and double check, and when you're ascertained, check once more!

Finally, when I'm feeling confident enough, I just make the connections, and turn the power on. Usually, there are some minor adjustments necessary (such as a contrast potentiometer), but other than that, LCDs work.