Here are tuner set ups on two of my boards. I chose these pedals for their reliability as well as the way they fit on each board. I have also used the Korg Pitchblack and TC Electronic Polytune Minis on other boards. Both great tuners as well.
The first uses the JHS Buffered Splitter. The signal is split immediately from the guitar input. One path goes to the tuner which is always on. The Boss TU12 EX is a remarkably accurate analog tuner. It is not appropriate for a lot of set ups as it is not really a pedal.
The second board utilizes a D'Addario Pedal Tuner. The signal path is split on the underside of the board. Again, the tuner is always on.