Each month, my goal is to have 25 short-story submissions out.
Understand, that doesn't mean I have 25 unsold short stories. Some are previously-published ones that I'm trying to re-sell. Others I've sent to five different magazines or anthologies; whoever responds first, gets the story. Only a few of the stories went to markets that specify "no simultaneous submissions." I don't like to send stories to those markets, but sometimes you have to -- they're the most prestigious, or they pay the most.
It's a lot of work to research 25 different potential markets. Even using Duotrope, it takes me an average of one hour to go through potential venues, find one that's appropriate, and adjust my submission to the venue's rules. Most months I don't get 25 out. But it's always my goal, and I'm glad to have accomplished it this month.