4. Grid design
This should not be a new one for you. Grid theory is maybe the most popular element of a composition, because we do it all the time even without realizing. Grids add structure to a design and are used to hold a good proportion among the elements on the page. You can find lots of grid frameworks on the internet, which are free to download and build on, and I actually recommend you to use them if you are a beginner in this domain. Working from the beginning with grids will make you feel comfortable with this approach and this is good for your layouts.
Grids do not have to be rigid all the time, they can also be subtle, but if you go for this option, then make sure the design will still be clean and refined before the delivery. When working with grids it is always a good idea to ask feedback from the ones around you, because working for hours long with a grid framework in front of you will probably make your eyes not see small mistakes that need adjustments.