Compared to other coding, HTML seems really easy. Hell compared to CSS, it is really easy! One thing to remember when coding HTML is STRUCTURE!!!! Structure is your best friend. You won't have a good HTML code, or a good CSS code, if your structure doesn't make sense.
Another thing to add on with having good structure, is coding logically. If your coding using a design from Photoshop or a screenshot to make a template, think about whether your sections align with your CSS code. Or if your CSS code doesn't have repeating codes.