Getting your initial tune for E85 done is pretty simple, all you need to do is to tell the PCM that it needs to use 33% more fuel. There are two ways of doing this “properly” without skewing other tables.

Adjust your base injector flow rate table to tell the PCM your injectors are smaller than they actually are.

If you're using Tiny Tuner, just go ahead and add 33% to the whole table across the board

There is a table you can find in Tiny Tuner called “Injector Skew Percent”. Typically this would be used to adjust for injectors that aren't flow matched perfectly. You can use this table to adjust for your E85 tune.

Just add 33% to each cell in the table.

There are a lot of people out there who complain about issues with cold starts in the winter using E85. This is an easy fix in the tune that a lot of tuners apparently aren't aware of.

All you need to do to fix this issue is to add more fuel during startup. There's a table called “Startup A/F Adjustment by Coolant Temp”. Go ahead and add 10% more fuel for temperatures 0*c and below, and also add 5% for 10*c.

All of this information was gathered from Frosty's post on the grand prix forums and tested on many of my own cars:
http://www.grandprixforums.com/pcm-tuning/94283-the-defacto-guide-to-tuning-your-car-for-e85.html