What are affirmations, you ask?  Affirmations are those things you mutter over and over and over again, sort of like a prayer, in hopes of procuring a desired result.  Is this a complex definition, full of ambiguous traps and pitfalls?  The short answer:  Yes.
    All right, here's an example of an affirmation.  You've been feeling really bad lately, all down in the dumps, and you want to change that.  You want to be happy.  Well, each day, you get up and say to yourself 3 times, "Today, I'm going to be happy, easygoing, and carefree."  Alright, so this is a common example, and which is heavily overused (it has even been made fun of on Saturday Night Live a few times).

    If I may, I'd like to delve into Psychology for a little while.  If you've ever studied Psychology, then you might grasp this better than others.  If you haven't taken a Psychology course, then I'd really recommend doing so, as it improves your knowledge of people in general, and Magick in particular.  Many things Magickal can be explained more readily using Psychological terms.
    All right, basic psychology tells us that what is repeated more often is more easily remembered.  It makes sense, right?  If you skip class all the time, then read the chapter the night before the test, what are the odds that you're going to get a good grade?  I discount, of course, everyone with a very good memory, "photographic"-quality even.  If we accept this (which we do), then where does this information go?  Using Freudian terms, this knowledge goes to the Id, the Unconscious.  How is Magick supposed to work?  By uniting the desires held in the Lower Self (unconsciousness) with the Higher Self (Superconsciousness, or superego).
    This is basically what affirmations do.  That's all there is to it.  "You are what you repeat".  :-)  Anyways, all I can give you now are a few more suggestions, then you're on your own.

Suggestion #1:  Keep your affirmations simple.  This isn't a prose-fest.  Don't use "I wish that each and every day my life will be touched as the sun touches the first drops of dew on the dandelion leaves in the height of Midsummer."  Use "Each and every day I will find happiness."  Even this is a bit long, because of Suggestion #2.

Suggestion #2:  Keep is short!  It's easier to remember "I am happy", than "I will be happy each and every day."  While the second one is okay, the first one goes into action quicker, and will sort of become your mantra if you think of it every day.

Suggestion #3:  Make it positive.  Don't use "I'm not sad."  There's too many negative words in there ("not", and "sad").  Use "I am happy."

Some Affirmation Ideas