I sort of agree with Mken, after fourteen months, sight reading for me is coming more naturally but I did specifically practice it. As your piano playing improves so does your music theory, and in turn so does your sight reading so this really is an interlinked and a stepped process. No need to rush out and learn a whole lot of theory that may not make sense or not even be needed for a year or so. So the first lesson is patience. Often the advice is just do lots of it, and this is solid advice as long as you don't try to run before you can walk. Sight reading as common sense dictates will always be behind your playing ability, so choosing material to sight read which is below your playing grade is key and one I have ignored a few times only to find I am wasting my time. So the next thing is to have lots of material. Some are free and there are a few site I sure will be recommended but I have four Denes Agay books which I find are particularly ideal for the purpose.
Both Joy of First Classics and An Introduction to Classics to Moderns are at the simple end (fourteen months on I am still at the simple end). Easy Classics To Moderns and More Easy Classics to Moderns I have but more advanced so will be future material.
Big Note books are also ideal – I have a couple, 100 Best Loved Piano Solos Vol 1 & 88 Piano Classics for Beginners. Also interesting to check your local library or second hand books store, bargain bins at music store etc for books ideal to your level.
I started with Prestokeys and I think it is a great program for the money. You can hook it up to your dp and set it so you can play along with it, plenty of adjustments you can make to make your exercises tailor made is also a bonus. However now I am using sightreadingfactory.com which has a yearly subscription (free to try) of unlimited exercises. Very similar to most exercise books (A line a Day or Paul Harris books Improve Your Sight Reading) except you have unlimited exercises and are able to access five different levels of difficulty. This program is not interactive (it won’t wait for you) but I find this better as in real sight reading there is no stopping. All exercises are computer generated and as yet chords are not included (but expected). Both programs and exercise books as well are only aids. You need to spend time with the program and real music and eventually you would progress past the programs altogther. Now I expect there will be a few who disagree with programs and exercise books but the programs are fairly new and I don’t think there is enough evidence to say whether they speed up learning or not, it’s just anecdotal and for me sightreadingfactory is the best so far and really helped me.
If like me you want to learn more about sight reading then this forum and the historical posts are just about all you need. I haven't found much in the way of books on the subject although I have a book called Super Sight Reading Secrets which is a method some love/hate and others like me can't get to grips with. It baffled my own teacher but she did say it had some good points.
So if you made it to the end here is your prize here
. A very ingenious forum member "supertorpe" has invented his own program which I just found today and on first inspection is very good.
PianoMarvel is also worth looking at (free to try) but is more of a complete learning system but because of it's interactive nature is ideal for sight reading practice.