Wide Angle Lens help

[curelightwounds]

I just started using my Sigma 10-20mm lens and I love it. Things are a little distorted in my shots but that's to be expected and not all that hard to deal with.

My issue is with making sure my shots are straight. Without a bauble leveler is there a way to make sure my shots are level? The shots are pretty level and again not too hard to deal with, but is there some trick to leveling shots through the viewfinder using a wide angle lense?

[IABoomer]

Does your camera have a grid overlay in the viewfinder? If so, you could use the gridlines to see if things were straight (or in the case of a wide lens with some distortion, that the straight lines are curved evenly from one side to the other).