New to kayak trolling...

Get a line counter reel. Learn how deep your various plugs run with each specific length of line-out. Don't run plugs faster than they were designed to be pulled. Going faster doesn't necessarily pull a plug deeper. Lipped plugs or crank baits will turn on the side and run shallower if you exceed the designed trolling speed.

Mount your rod where you can see its tip, so you'll know when you get a hit. Mount it where you can grab it easily out of its rod holder. I mount my trolling and downrigger trolling rods on a geartrack on my left gunwale, pointing to the right across my kayak, at a right angle to the centerline of my kayak. I position the shaft of the rod a few inches behind my left toe when my left pedal is all of the way back. Neither the shaft or the butt of the rod interferes with pedaling in this position, it's easy to put the rod into and take the rod out of its rod holder, and its easy to monitor the tip of the rod. I mount my fish finder on my right gunwale, so I can keep an eye on it and the tip of my rod at the same time.

I don't use extenders which raise my rod holder up above the gunwales of my kayak. They put extra stress on the base of your rod holder and the hull of your kayak.