Here are 10 tips for Piano Sight Reading Grade 1 - 5 (taken from the January 2019 EPTA magazine article by Karen Marshall)
1. Each exam grade adds a new skill
2. Learn to identify intervals in your music - name notes out loud
3. Pulse maintenance
4. Try not to correct yourself
This is really hard but really important for sight reading.
5. Rhythm skills
Multi-tasking pitch and rhythm at the same time is hard.
6. Key awareness
Get to know which sharps/flats belong to which key signature.
This helps you to map your way around the keyboard more efficiently.
7. Try not to look down at your hands
8. Bass Clef Reading
Everyone finds reading the Bass clef more challenging than the Treble clef.
9. Expression and articulation
Before you start, look through a piece and see if you can memorise or point out on the page the dynamic markings on the page before you start playing.
10. Play anything!
The more you pick something up that you haven't seen before and try to play it, even if it is only playing one hand instead of hands together, the better your sight reading will become. There are lots of free sheet music websites on the internet.
Practise makes perfect!