1) If you're still stuck on the first riddle, just read it more carefully. It really isn't that hard.
2) Read the FAQ. Some of your questions might already be answered.
3) Take notes. It would be a shame to have progress on a riddle and lose your train of thought. Brainstorming and writing down ideas will probably help you.
4) Use Notepad. Some of the riddles are much easier to solve if you copy and paste them into Notepad. That way you can rearrange the letters.
5) Check the forums. Seriously. Most players share their answers by giving good hints, and since some people are most likely ahead of you, these hints (or even answers) can easily be found on the forums. If there aren't any hints there, post a new topic.
6) Use Google. Google is the ultimate place to find answers to almost everything.
7) Ask some of your friends. Between two or more of you, there is a much higher probability you will find the right answer.
8) Join an existing team, or start your own. Many players have formed teams to group their efforts and share knowledge.
9) Sleep on it. Maybe you'll have more ideas tomorrow. A good night's sleep will do wonders for your concentration.
10) Have fun! This is the most important tip of all. This contest was designed to stimulate your mind. Sure, you might get frustrated and over think some riddles along the way, but don't forget that this is only a game.