As Tom says, put it on a timer, hat way your not having a slight wobble when pressing the shutter. ISO is prberbly best around 200, thats what i use anyway. Check your file type. I know on my 350D you can select fine or medium quality JPG, i wouldnt bother with RAW.
You really need to sort your metering out. On the 350D, multy segmented gives the best results, with regards even high lights,shadows and color rendition. Again, check your white ballance too, AWB, is usualy best but shade and florecant can work well too.
I shoot in auto, but use the selection points for making my focus points. Your apature may have something to do with your blur. If its very low like f4 ( AV 4 ) then there will only be a very small section in your picture that looks sharp, and if that section is in open water or in a shaded area, then you wont see it.
Hopefully youl get it sorted mate.