#1, set your camera on tripod, put something at where you suppose to pose, focus on the things and set camera to manual focus to lock focus, remove the thing, start self timer and pose.
#2, compose your shot with tripod, dismount camera, pose where you are with the camera, focus on the tripod base, set to manual focus to lock focus, mount the camera on tripod, start self timer and pose.
Closest subject priority AF will also help in many situations. Most of the time when you do self portrait, you are the closest subject. You don't have to aim the focusing point at anything, your camera will determent the closest subject and focus on it. Do maintain enough DOF, your camera may not be focusing exactly on your eyes, but you want your eyes to appear in-focus.