Pour some liquid from the starter bottle into the beer bottle, shake around to oxygenate and stir up the sediment, and pour back into the starter bottle. A couple of transfers back and forth between beer bottle and starter bottle help oxygenate the beer further as well as getting any extra bits of yeast out. Put the airlock back into the starter bottle. I find that Spitfire yeast should be going well and ready for pitching after about three days. Drink the beer in the glass.
Some people use the yeast from two bottles to prepare their starter.
I have not found this necessary.