Im with Sandra on this one. I wish I knew how to write on cakes. I can not write on cakes....the harder I try the worse it is. So I will take any suggestions that you all have. TIA MC
This is a copy of a handout I give to my Wilton students when we do the section on writing, maybe it will help you as well....
Helpful Hints - Writing
The best thing you can do to help your writing is PRACTICE by writing on cakes whenever you get a chance to.
Other helpful hints are:
1. Use Message Press Sets - Wilton offers several of theses.
2. Use the bottom of your cake pan to plan, space and practice your lettering.
3. Maintain a straight line by using spatula or toothpick markings.
4. Relax and move your whole arm, not just your wrist, to write effectively.
5. First write the message in the same color your cake is iced in then pipe over it with a second color. You can also pipe it first in clear piping gel.
6. Get different font ideas from your Word Processing program on your computer.
Print out your message using a font that you like. Using a corsage pin or toothpick, poke holes along the letters. Lay this over the cake and dust with powder sugar or cocoa powder. When you remove the paper you should have little dots that you can follow when writing your message.
Remember, spelling counts! Write the message or name on paper first to check it.
An additional thing you can do is to print out the message, reverse it then lay a piece of glass or hard clear plastic over the message. Trace it using royal icing and let it dry. After it is dry you can turn that over and use that to imprint on your cake to follow as a guide. 
I always use the piping gel technique taught in the Wilton Course 1 class.
Type up your message and print it out mirrored (I'll list how to do this in Word below). Place wax paper over the text and use piping gel to write the text on the wax paper. Turn wax paper over on to cake and gently run your fingers over the gel. When you remove your wax paper, a bit of the piping gel will remain behind. You can then pipe over this with your icing!
I do recommend you practice this once or twice to get the hang of it.
How to print a mirror image in Word:
Go to File --> Print
Click Properties (top right)
Click Features
Select Mirror Image
Hit OK to get out of the Properties and to print the sheet
I use the "Tempus Sans ITC", "Bradley", "Papyrus", "Andy" & "Curlz MC" fonts from the Microsoft Word program as my inspiration.
They are freeflowing and fun...almost "scribbled". My clients seem to love the style and always request my "fun printing...not cursive".
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