I've hunted them ~10 years in a row in NW Nebraska, all DIY, on a mix of public and private land. Success rate has increased over time. If you're going outfitted, the OF will have all their patterns figured out, but for a DIY, here you go.
First advice, get high in elevation late afternoon and glass where they roost. Once they roost, they are very vocal and will gobble at anything - fake coyote howl, whistle, train, car horn, you name it. Use that to pinpoint their location and devise a setup plan for the next morning.
In general, I've not had good luck calling them in. Some people have, but not me. Birds can get call shy easily if they've been called to. Our best strategy has been to figure out where they are headed from the roost and setup a couple hundred yards that direction, and wait.
Another successful strategy we've used is what we call a push call. If you see them drop into a canyon, set up a stationary shooter, and a pusher. Sorta like a deer drive. The driver calls lightly and works the canyon. The turkeys go away from the caller, towards the shooter. The key is to move slow and allow them to walk away from the calling before getting spooked.
In NW Nebraska, their tendency is to pitch down at daylight, and feed along the canyon walls. Somewhere around 10-11, they drop down into the canyons/creek bottoms and stay there until a couple hours before sunset. You may catch some out in the middle of the day, but with early morning sunrises and late evening roosting, we take a break during the middle of the day, eat our big meal, take a nap, and head out again around 4 pm.
You'll hear people say Merriams are nomadic, well, they are, but not from day to day. In other words, where they are on Saturday, they won't be far on Sunday, or Monday. But if you come back two months later, yea, they'll have moved on.
Good luck and post some pics!