Two easy options come to mind:
1. keep an eye on blockchain.info and take your miners down when you see Slush get a block.. it updates automatically and there should be a fairly short lag.
2. Keep refreshing the stastistics page until you see "Current round duration" reset.
Since 1 is less likely to cause issues for the pool.. I'd go with that
The network has gained 50 PetaFLOPS in the last few weeks so I'm having a hard time telling what pool works best for me.
Since most pools use systems which discourage hopping your best bet is to leave your miners on a single pool (or point each of your individual gpus/whatever at a selection of pools) and leave them alone. If you're that bothered by the variance you should pick a PPS (pays the same per share everytime) pool.. although in most cases you'll pay a higher fee to the pool for the privilege.