Sometimes, actually WRITING out affirmations can be even more effective. You're saying them and writing them, so you get a double whammy of energy. What I have found to be effective is to also write around 100 of them in an email to yourself. Do them in block capitals, and do them in blocks of 4, but with every eighth block, change the colour of the font. The effect is that as you scroll through them, the sudden change of the colour acts like a subliminal message in the cinema, and stuns your subconscience, into reading and them absorbing the affirmation and its meaning.
A further thing you could do is to make a print-out of your chosen affirmation, in black capital letters on a white background, so that it looks like a newspaper headline. These are always written in this way so that the message goes straight to the subliminal mind of the readership (usually about something bad). You can do this for a positive message which you would really like your mind to absorb, and if you put it in an obvious place (preferably at eye level) that’s what will happen.