One of the most common errors you will see in your daily reading is the incorrectly-formed posessive noun. This is an odd truism, given that there are only two rules to forming posessive nouns in English:

1. If the noun is plural and ends in an "s", then put an apostrophe (') after the noun
2. Otherwise, put an 's after the noun.

Simple, huh? But people get it wrong all the time. Here's a great example I just saw:

I love football. On today's game, we have many graphics telling us about "Simms' Spotlight", a set of things that announcer and former New York Giants Quarterback Phil Simms thinks the teams need to do to win. Now, there's a grammatical error in that big 'ol card shown on TV.

Look back at rule #1. Does Simms end in an s? Yes! Is it plural? No! It's a last name! (Even if Phil's last name were, say, "Trees", it would still be singular.)

The correct way to form the possessive of Phil Simms's last name is as I just did, Simms's. It looks a bit odd but it's correct. Now, if Phil's son, current Tampa Bay Buccaneers Quarterback Chris Simms, was also giving his opinions, then we might have "Simmses' Spotlight", because we'd be talking about the Simms plural, or Simmses, and then we would have a noun ending in an "s" and which is plural.

Don't even get me started on forming plurals incorrectly