When we got to 12U the 1st and 3rd send the runner from 1st was pretty standard move. Saw all kinds of ways teams tried to stop it. Throw to 3rd, crashing MI, back to pitcher, pump fakes etc. We did them too.
I said to our head coach at practice one day, Since on a lot of these plays runners don't get especially good jumps because they don't want to get picked off and don't expect a play what do you think would happen if we just threw it through to get the back runner. I said we will get outs instead of 2 in scoring position. With 2 outs we can end the inning. We told our pitcher to fake like he was catching the ball to hold the runner at 3rd.
Next tournament we threw out 4-5 runners and killed innings. The look on a few of the runners face was pretty funny. They never expected the ball to show up and had been running wild for a couple of years that it was a total shock for them. We gave up a couple of runs but actually caught a few napping on 3rd and held them there.
We knew we were on the right track when one of the guys we coached against who had been a MILB up to AA I think and was always one up on us said after the game...I guess we aren't playing kiddie ball anymore.