Sometimes you want to style the first letter of the first P element a DROP CAP inside the WordPress content <div>. The CSS way to do this is something like this:

Code:
.entry > p:first-of-type:first-letter {
	/* style your DROP CAP here */
}
Wherein .entry is the class name of the WordPress content block.

first-of-type selects the first of a certain type of tags, and first-letter selects the first letter inside the element.

When there is an image <img> inside the first P element proceeding the first letter, this approach will not work. Instead, you may consider capturing the WordPress content output so that you can search it and add <span class="drop_cap"></span> around the first letter, using preg_replace.