I have a twice-monthly routine for checking on submissions, and it just so happens that this Thursday falls on one of those days, so I thought I'd take this post to talk briefly about the business end of writing - or at least, the submitting end. So - dry deserts ahead!
I have my own system for submissions that's always worked well for me. I keep approximately eight stories and three pieces of flash fiction or poetry in circulation at any one time. (Obviously, there's some overlap in the markets, but there are enough venues that accept only poetry and/or flash, and conversely venues that don't accept it, that I feel justified in running separate "tracks" here, as it were.)
If a story is rejected, it goes right back out again unless:
1) There's a particular place I want to send it, and they're currently closed to submissions (or I already have a piece there); or
2) I receive commentary that I feel is merited and decide to make the changes.
For agent querying, I start with three queries, and every time I get a response, I send two more out until I have a total of a dozen (at which point I go back to 1:1). This ensures that I'm not trying to do a ton all at once. At least, that's the idea: I've only done this organized plan the once, with Journal of the Dead, but it's worked well, so if I have to keep querying ... at least I have a process.
As for the twice-monthly routine, it's to check up on all this. I go down my tracker, check the response times of the market (or agent), and if it's been significantly over the listed amount of time, a receipt query letter goes out. (With agents, I'll send an inquiry only if their website doesn't state that they don't respond for rejections, obviously. ... oh, wow, there were a lot of negatives in that sentence.) I figure out "significantly" by something between formula and gut feel - proportionally more time for markets that have a longer lead-time to start with, if I've worked with a market before and know they're a smidge slower than advertised .. etc.
So that's submissions side of it for me.