It's important to understand what catches a user's eye first on a page, then second, etc. If you know this you can order your page elements accordingly.
There are several factors in what captures a users attention. These are size, contrast, movement and position.
This is obvious but a user will see a larger headline before a smaller one. This is why we use larger font sizes for higher impact. Making text bold or not has the same effect. Similarly, a large image will be seen before a headline so decide what you want to be seen first. If it's a headline before an image fade the image in after a few seconds.
Contrast is also a factor. If you have text on a white background and some is pale blue, some is black, the black text is read first. Order the sections on your page by setting the text colour for the desired level of contrast.
Movement grabs attention. If you want someone to notice something animation is a strong way to grab the user's focus. Add movement to text or images if you want themn to catch the eye. This can also work against you. Do not have animated ads on a page where you want the user to read your copy - they will get distracted.
Finally, positioning is important. The eye naturally focuses on the middle of the screen, not the top left. If you want something to be seen first, place it in the middle of the screen. Combine this with size and contrast to focus the user's attention where you want it.
