It seems to work better if you have other people (or a people substitute) to play with. That way, there's feedback between the eyes and the ears.

If you can find someone who reads music already and will play with you that's good.

If not, get a music program on your computer, have it play tunes, and play along with it. As your eyes scan the notes, you will hear the timing they produce.

What instrument are you trying to play? Spring for a few lessons.

Don't tell me you are trying to sight read for singing. That's really hard.