Question about making a starter

In most directions for making a yeast starter that I have seen, they mention using DME for the starter. If I only have LME for the current brew that I'm making, is it fine to use that for the starter, and if so how much should I use?

I made my last starter with LME but I don't know if I did it right. I took a sprite 2 liter and sanitized it, put some hot water in it and added a little bit of LME. I put an airlock on top and shook it every once in a while for a few days before brewing. There was no activity in the airlock, but I shook it and pitched it anyway. I don't usually get activity the day I brew, but that night it was bubbling happily. It has another week in the fermenter so I don't know how it will turn out yet. Hope you get more responses though, I would like to know the right way.