When first looking at a piece of music, take an overview of the entire piece before playing a note. Note the time signature and key signature in which the piece begins. Then look for changes in time signatures and key signatures throughout the piece. Also, look for dynamic changes throughout the piece. Look for rests within the piece as well, so you won't be surprised by them.
Looking one measure or two measures ahead as you play can make sight-reading easier due to knowing what's coming next in the piece. Practice this by playing one measure slowly and looking ahead at the next measure, playing through the measure without stopping.
Keeping an eye out for chromatic passages (paying special attention to what notes they begin and end on), note intervals and chord shapes (outlines of chord triads or seventh chords) will make reading them when they come up easier. If you already know what those look like on the piano, you'll play through them more easily when they come up. Keep an eye out for accidentals (sharps and flats) in the piece as well, as they may show up in the piece, regardless of whether the key signature has changed or not.
Look at the rhythm of the piece and identify rhythms that look difficult. Sing them to yourself in your head before playing the piece. Internalizing them before playing them on the piano will help. Also, see what types of rhythms repeat throughout the piece (for example, quarter note triples, eighth note groupings) and keep those in mind when you play through the entire piece.
Once you've analyzed what's on the page as much as possible, playing through the entire piece without stopping is the final step. During short rehearsal time, no rehearsal time or auditions, being able to play through an entire piece in one sitting is required. Make sure to pick a tempo that is a slightly slower then you might be able to play the piece. You'll feel more confident playing slowly and correctly than too fast and missing notes and rhythms throughout the piece.