Easiest is to shoot with a focusing screen with a grid. I also use a simple grid lined paper (graphing paper style) that I custom make from this great website: http://incompetech.com/graphpaper/ you can input the sizes you want for the grids, and choose whatever style you like, from standard boxes to triangles, and print it. I drop this graph paper onto my easel, align it with my blades on both sides, and use that to help get nice straight lines in prints. For lots of tripod work a nice bubble level makes things easier. I use a simple inexpensive 3 axis type and it works fine. there is also a digital LED level with blinking level indicator lights for I think $30 bucks which might also be a nice investment if you use it a lot.