We had a couple of one week hires with friends a few years ago and that planted the seed. Real planning only started with the thought (12 months ago) that we could (i) retire in 2014 and (ii) probably/possibly/hopefully afford our own narrowboat.
The planning has mainly been around the financial side given not only the purchase costs but also that I reckon we'll need (boat's not ours yet still awaiting survey) £4k-ish pa for running costs (£2,400 mooring, CRT license, insurance, RCR recovery, annual service, blacking/anodes every 3 years) - as well as a contingency fund 'just in case'.
I guess there's been a lot of other 'planning' in terms of looking at boats, talking about what we both want, finding things out on the internet, etc but that's been fun.
Steve