I did mine Part 61, independent instructor, renting from a large flying club.
Before I started the flying portion, I spent about 6 weeks home-studying for the written, with heavy use of Sporty's Instrument Rating DVDs (they were a new offering at the time). I passed the written a couple/few weeks before I started the flight training.
I started my instrument rating instruction with a few hours in the plane, then a mix of sim and plane (using the sim to polish procedures), then back to just the plane for the last 15 hrs or so. I finished the rating with about 46 hours of instrument training, which was really less, because about 6 hours of this was simulator and hood time spread out over a few previous years. 20 hours of this were in the simulator. There were also quite a few hours (ok, probably over 100) messing with MS-flight sim in "instrument conditions" for a few years too.
The training was "concentrated" as much as I could within a 2-1/2 month period, while working my regular 40/week (probably took a couple/few days off of work), flying/simming about 3 times a week, on average.
All of the ~40hrs during training were with an instructor (no hrs w/safety pilot-type time logged). All time was with the same instructor, except one informal phase-check type ride that I requested to fly with another instuctor late in the training.
It was a tremendous amount of work, but also a great sense of accomplishment once it was done! If I had to do it again, I would do it exactly the same way. What works for some doesn't work for all though, and you need to evaluate your individual situation and learning style.
Good Luck, and have fun with it!
Jeff