leave the lower triple tight, but loosen (but not remove) the upper triples and the axle.
Now push the bike against a wall or other firm structure and bounce the front of the bike up and down without the wheel rotating.
The telescoping of the forks will help them return to parallel, or as parallel as they can be.
Now tighten up the loose stuff and look things over carefully.
Another possible test is to find a piece of plate glass and lay it across both forks above the fender but below the lower triple.
See if the glass rests on both sides evenly or if you can rock the glass on diagonal corners.
If the plate glass won't lay flat, something is tweaked and you need to fully disassemble and check.
(the glass from a picture frame may work for this)
If you must disassemble, the first thing to check is if the tubes are straight.
If you clamp the lowers in a vice and rotate the top tube in the lower, you may be abel to see right off the bat if it's straight.
If you can see a wobble while rotating it, that's bad.
The preferred way to check if forks are straight is to completely remove the tube from the lower and spin it in a cradle to check for true.
If you don't have a cradle you can take 2 yard sticks and lay them on edge on a table then roll the top tube along them for the entire length and see if you can see a wobble. On chrome tubes the human eye can pick out an imperfection of a tenth of a millimeter easily.
Best of luck!
