The first thing I look for in a potential cell building colony while I'm performing Spring inspections is size. When I pop the top, I don't even want to see much frame. It needs to be black with bees. The first thing I think when I see a colony that size that is crowded is, o no, they're going to swarm. That's the perfect colony! Why? Size equals resources. And they're already in the mood to rear queens. When the population approaches that size and the colony is becoming increasingly crowded, it triggers them to rear queens. They're in the mood, and have increased brood production from incoming nectar and pollen. The bees are programmed to know when to rear queens. A period of abundant nectar and pollen will ensure the queens will be well fed, and if a swarm is issued will strengthen it's chance of survival. The timing is no accident. Once I find a colony of this size, preferably wanting to swarm, I remove the queen. I typically add her to a small nucleus colony "retirement home" to keep her available for grafting daughter queens. I like to rear from robust mite resistant colonies. They also must be free of any brood diseases, or obvious issues. After removing the queen I graft very young larvae into queens cups. I add the cell bar frame with the new grafts, top off the feeder, and I'm off. The grafts can be checked at any time, but I normally check them on a weekly basis while removing the cells, and replacing with new grafts.