Every good designer has a well-calibrated "design compass" that comes from constantly looking at good designs
magazine like HOW or print
Without a good "design compass," no amount of Photoshop filters will save you
align
typography
great website with only a little color and great type
(a) busy websites can be ineffective, (b) "whitespace" is not just a fallback for lazy designers, and (c) the so-called "empty" portions of a site are necessary to set off the other elements.
critique
There's a reason that these people are designers (and get paid for it) while you are not.
"No Need to Get Too Detailed"
Most programmers scoff at the idea that a designer might spend several hours choosing exact colors for a website.
colors will always matter more than you think and you can't change them after a site is being built (at least, not without great effort).
Not Paying for a Picture