First time with a DSLR. Need some advice.

[RamJam]

I just got a second-hand E-510 a few days ago, and read up on ISO, Exposure, etc. I've always used a point a shoot, so im just playing with a lot of random settings for shots here. I tried out some stuff that was in the books, but it seems like im over exposing it all the time.:x Is there anyway to fix it? (I always feel like it looks good on the preview but when i stick it on the computer it looks el horrible

Thanks guys!