First go to http://www.mapquest.com
and get yourself a map of Northwood, Ohio. You can also get directions from wherever you are coming from.
Assuming you are coming from I-75, get off at Wales Road and go east. When you get to E. Broadway, Wales appears to end but take a left and you'll see it resume on your right hand side.
Vickers crossing is at the corner of Wales and Droulliard Roads, you can't miss it.
The diamond is of course not legally accessible but people do drive along and park on the gravel roads that lead to the crossings, both from Wales and Droulliard. There used to be a vacant building in the northeast quadrant of the two roads where people could watch from but now this facility is a small business, I think auto repair so I would imagine it too, is off limits.
There's lots of trains here but unfortunately you can only really watch legally while driving.