I haven't had any major experiences that you could say were UFO's. There have been many times in my past when I would look up into the night sky and wonder what was out there. I rememeber several incidents when I would watch planes fly across the sky and sometimes I would watch as they would move extremely fast in odd patterns. Were they really planes or were they UFO's? If you're not convinced that they might have been UFO's let me add this. As I watched and sometimes saw the objects flying in odd patterns, I would watch as they would dissappear instantly.
One time I was watching stars and I watched one get bigger and bigger until it looked almost the size of a golf ball, now you have to think when you look at the stars they usually look like far away dots. This one was golfball sized, I think that it could have been a UFO flying close to the Earth. As I watched it after about 4 minutes of it beeing big it started to get smaller and smaller until I could no longer see it.
I know that these may not be UFO's, but I have never seen a plane move in odd patterns in the day light, and I have never seen a star enlarge and shrink in a time frame of about 10 minutes again either.