You'll need a fast and accurate thermometer. I use the Thermoworks Thermapen, which is fantastic in reading the meat's internal temperature.
You should also invest in a set of Grill Grates. They make searing on pellet grills much easier and help achieve pro results. Don’t worry, there is a set that is made specifically for whichever Grilla Grill you have. The grate is able to amplify 500 degrees to about 700 degrees on average, which is a great temp for searing steaks.