Flower Friday

This darling trailing geranium has been outside in the summer sunshine since the spring.  I overwintered it fed it and turned it out.  Basically it has lain dormant all summer.. not grown much and not flowered .. that is until I brought it inside last week.. suddenly flower buds appeared and now it is in glorious bloom.. on my kitchen windowsill.  I am sure this is not common behaviour for a geranium... are there any successful geranium growers out there that can help let me know what I need to do to get more growth and flower next year? Should I prune this one which is now two stems which grow in opposite directions for about a foot each? and when?
The flower is so pretty I would love it to show more of them.