Editor Betsy touched on this in her recent post but it is worth repeating: cut out all extra bits in your short stories. Cut, cut, cut!
I freely admit this is tricky. In a story I've been working on for like a year, my critique group said recently, 'you know, you don't need this scene'. I looked at it, and they were totally right! So, perhaps I'm changing my point to: critique groups are vital.
I could summarize the whole 300-word-ish scene with one sentence! Jeesh! You'd think an editor could see this on her own. But no. It is difficult to truly see your own writing. All authors need to be able to step back from their work and try to see it objectively. So, wait, that's my point: step back from your writing. :)
Okay, I'm rambling a bit. That's okay on a blog, but NOT in a story. Maybe that's my point: don't ramble.
I'll stop now. :) But please continue to send Electric Spec your excellent (succinct/non-ramble-y) stories. Thanks!