Remember: This is still an alpha. The game isn't fully optimized yet.
Also; if you have a Nvidia card (MSI preferably), download MSI Afterburner. It gave me a steady 10-30 fps boost. You just need to find the right settings, and you'll definitely see an fps increase(Assuming you have decent CPU that won't bottleneck). Afterburner is also one of the safest overclocking software available, as long as you don't play with the voltage. There are tons of guides, just google it. And as i stated in my previous post: I highly recommend Game Booster. It will close any unnecessary applications that may slow you down. You may also want to lower the Nvidia Control Panel settings (under "Manage 3D Settings").
You can also Ctrl + alt + delete and open the Task Manager, then right click on Arma3 and set the priority to high. Don't use Realtime, though.