Synchronize your clock with a time server, submit your txid at 1 second past the whole hour.
I use this on a (Linux) console (it shows the time 5 times per second):
while test 1; do date; sleep 0.2; done
If I click "Submit for FREE" at 10:00:01, it's added to the queue at 10:00:02.
This usually works for me.