How to retrieve an element within several tags by tag name for selenium automated testing

I'm creating an automated selenium test using org.openqa.selenium.By to grab certain elements on the webpage that is loaded but I get nothing back when I'm searching for some elements. This is probably because the element I'm searching for is within several HTML tags? I put this code in the browser console just to see if I could see the tag I'm looking for listed but I only get back a list of top level element tags.

var all = document.getElementsByTagName("*");

for (var i=0, max=all.length; i < max; i++) {
     console.log(all.item(i))
}

Would anyone know of a better way to get an element using selenium since just By.tagname(tagname) doesn't work?