Speed speed speed
Your pages must load fast. If they don't load fast they won't rank well. Mobile users won't wait.
Don't bloat your pages with sales and marketing fluff. Be concise and descriptive with your copy. Remember that search engines can do inference like a human brain. So you can't rely on the picture and artwork. Its all about the copy and the keywords contained within.
Everyone knows navigation should be intuitive and simple. As soon as anyone says simple expect effort to get there. Things to work on are making sure there are no dead ends. Every page should have a couple ways out. Work on 1-2-3 rule one step to get anywhere great, 2 steps ok, 3 steps is the limit.
Compress and size your images
Compress your images with something like minijpg or tinypng. Try to use jpg more where possible as they compress better. Resize your images, for example if the display is 100x100 then resizes to this or close. Don't use a 1200x1200.
If you are lucky enough to have server side compression and resizing like cloud.mebsites.com hosting does!! then all the better, but you still need to do it.
Match your colours
The human eye, for most of us, has a great ablity to pickup contrast and disparty even when its minor. Consequently guessing colours match isn't quite enough. Use a proper colour matching wheel like adobes use it. It'll lift the look of the whole site when you match it all nice.