My niece wants me to write a very long poem on the sides of her 3 tier wedding cake. My penmanship is not very consistent. Anyone have any ideas on how I can make the lettering look more professional?

There's a free Craftsy class called "Hand Painted Cakes".  It covers a technique used to transfer a design onto a fondant covered cake.  You could do that with the writing, and then hand paint over it.  Should work beautifully!

hmmm....wasn't thinking of hand painting it, but that is an idea!! That may be much easier that using royal icing or butter cream to create each word. The entire cake will be covered in words, all the same font and size. It needs to look very neat and straight. Thank you for that suggestion, I will look into it.

honestly, i think hand painting the letters will look much nicer than piping it on.  I'm too lazy to look for some examples, but there are a lot of cake pictures where the letters were painted on and it looks very elegant!  

don't forget the tappit letter cutters if you have the room

ASavanah Cakes has a you tube on how to transfer a monogram. It would be time consuming, but I think it would give you a good option.

AYou could try wafer paper. Print the poem with an edible ink cartridge onto the wafer paper & attach to the cake with a little corn syrup. Google for tutorials! Hth

I did the words on this cake with tappits, it was time consuming, but much better than trying to consistently  pipe it. Also the edible image idea will work.