A rough and ready check is to use a string line.

If you take a string line from the rear tyre to the front, as it touches both edges of the rear tyre, it should be parallel with the sides of the front tyre. The handle bars and forks should be pointing straight ahead.

Possible issues to look for:
1) rear wheel not adjusted square in the swing arm.
2) Front forks twisted in the triple clamps
3) Frame twisted (worst outcome)

Note: If you do this on both sides of the wheels, you might find the rear wheel is mounted on the bike with an offset. As long as the measurement at the front tyre is the same for each side.

I haven't done this on my Tenere as I spent $1K getting the frame straight, so expect it is...

Hope the sketch makes sense:

Wheel alignment by DARREN MORRIS, on Flickr