Getting myself in focus for self portrait shots

On many occassions  am looking to take self portraits posing in front of landscape/scenery or monuments. With nobody around, I use a tripod, set 5 to 10 second timer and pose in front of the camera. My difficulty is in getting myself in focus. How do I ensure that I am in focus? When I frame the shot viewing from behind the camera, I do not know where to focus. And once I press the shutter release full way down (and start the timer) the focus is locked and is not going to change once I appear in front of the lens. I know using a remore shutter will help, but unfortunately my camera, the Sony Nex F3 does not support remore triggering. What do you suggest, or am I missing a simple trick?

One thing to keep in mind is that I wish to pose a little further than arm's length, so I really cannot stan in front of the lens and trigger the shutter release. Many a times, I wish to appear smaller in the photo and therefor wish to pose a little furher than arm's length. This precludes the possibility of focussing by standing in front of the lens. Suggestions are tips are greatly acknowledged and appreciated.