We do not plan that carefully, and even when we took longer and more difficult trips (read that: when we were younger and in better physical condition) we really didn't.

First we choose a date and decide how many days the trip will be.  Then we pick an entry point based upon how many travel days we expect and if we want to have layover days.  We always plan for at least one layover day/wind day, sometimes more. 

We do sometimes read information on portages on our planned trips, but never about campsites and we never plan to stay at a particular site.  Sometimes we have hoped for one, especially if we were repeating a lake and want to stay at a remembered site that we liked a lot, but that usually doesn't work out anyway.   :(

I really prefer not to have information about the campsites, as I like to be surprised when I see them the first time.

We only take the standard Fisher or McKenzie maps and don't take a GPS or make itineraries ahead of time.

Actually, now that I think about it, our planning hasn't changed hardly at all in 42 years.  That's sort of scary, isn't it? :-/