Use the simplest code possible

It's easy to get drunk on the power that new techniques afford us. With this in mind, aim to solve your responsive problems in the simplest manner possible. For example, if you need to style the fifth item in a list of items and you have access to the markup, don't use an nth-child selector like this:

.list-item:nth-child(5) {
    /* Styles */
}

If you have access to the markup, make life easier by adding an HTML class to the item:

<li class="list-item specific-class">Item</li>

And then style the item with that simple class:

.specific-class {
    /* Styles */
}

Not only is this easier to understand, it gets you wider support for free (older versions of Internet Explorer don't support nth-child selectors).