I'm going to put some Special Effects cupcake pink in my hair in a few days, but I tested it on one of my pale blonde human hair clip-ins, and it's brighter than what I want... so I want to dilute it with conditioner when I use it on my own hair. I want a pastel "strawberry ice cream" pink like the example I attached (I found the picture in the pink hair group on livejournal)... what ratio of conditioner to dye do you recommend?

Lots and when you think you've used enough, add some more.
The colour of the dye should be pretty close to the colour you want your hair. When I do pastel I mix it a bit lighter than I want the desired colour to be. Light colours tend to "develop" a bit in that they start to look darker after sitting on the hair for a while so that's why you need to go light. Another point for going lighter is that you can always reapply to darken it but if you go too dark it's going to take a week or two to lighten.

I' d love to see your final results :D I wish you luck =)