This has probably been written about many times but I couldn't find anything so here we go again
I will be doing a cake soon that is going to have vertical stripes placed on one of the tiers. I am seeking advice/tips that anyone might have on keeping everything straight. The stripes are going to be spaced apart from each other so I can't rely on butting them up against one another to keep everything in line.
I'll probably be ok but thought it was worth asking just in case someone has an easy way of getting it right!

cheers!

I would just use a long plastic ruler that I can rest on the counter while I'm decorating it and just place it up against the stripe when you've positioned it. I've done it this way when I've needed to use vertical stripes.

After you have rolled out the fondant to the correct thickness let it sit a while and dry then cut your strips and let them dry a bit so they don't get all wobbly,then attach them.

You'll be amazed how well you can do eye balling. The black and white cake I eye balled. I always place the middle stripes first, the 1/2 between then 1/2 between again. If you want to have the distance between the stripes the same width as the stripes. Make a stripe and let it dry hard and use that as you guide so you can have something to place it next to.

i've been wanting to get one of those 5 wheel pastry cutters. that's what i see them use on tv and would save so much time!

Not sure if this will help but have you thought about using the tile spacers they use for tiling.
I find using these really help to keep your gaps consistant.
You will find these at Home Depot in the tiling department.