The complicated story says people pay attention to color, textures and effects, typefaces, complexity, and layout and positioning, in that order.
The simple story says, make sure you look like you belong in the conversation. This is a focus on your audience- it does not matter what your opinion is of what you should look like. It matters how your audience expects you to look.
It starts with audience, which you know about from step 1, know the room. What do they care about. How do they see you. THIS IS NOT ABOUT YOU. Most websites are extensions of their creator’s ego, and those are the sites that make me cringe.
Think about how you want your audience to feel. Excited? Reassured? Sold? Your design and your language decide this.
Copying what works is, as always in web marketing, very valid. Think of men’s fashion- always stay the same. Think of women’s fashion- a race to see who can copy who the fastest.
So before you design your site and your marketing, stop and think, are you doing this to satisfy your ego or to make more sales?