Memorize where the notes fall on the staff. The first step in learning to read music is to learn the staff so well that you no longer have to think about it, so start with the pneumonic devices (like Every Good Boy Does Fine and F-A-C-E for the treble lines and spaces) and practice until you don't need them.
Write the note names inside of the notes when you're first learning so that you don't have to use the pneumonic devices, which can slow you down. As you remember the notes and don't need the labels anymore, erase them.
Practice music that has notes progressively farther away from the staff. Find music that includes notes only one or two ledger lines above or below to begin learning the notes outside the staff and gradually move to even higher and lower notes so that you don't always have to stop and count.
Memorize common rhythm patterns, like syncopation and various combinations of eighth notes and sixteenth notes, so that when you see them, you can recognize and play the rhythm without having to count the individual note values.
Utilize chord progressions to recognize key changes and notes more easily. If chord progressions are written on the music, use them, and if they aren't, consider writing them in.
Follow similar patterns and lines when reading sheet music or a score. If you're reading a score, look for similarities among the parts so that unique parts stand out more and you can pick them out, and look for lines that repeat later with the same or different instrumentation.