One thing that I need to do more of is practice sight reading in keys other than C. A lot of method book, keep you in C for a long time and then only give you a couple of songs in G, F and maybe D. Once you learn these songs, it's no longer sight reading and becomes mostly playing from memory. From there the difficulty increases rapidly whilst new keys are being thrown at you.
What is needed to get better at sight reading is just lots of practice fodder material. I'm compiling a list of really easy stuff to learn that is listed by key. I think that I will stick to a certain key for a whole week and get used to playing and reading it before moving on to a new keys.
A good resource is this site...
....where you can search by key and level and find pieces that you can play at your level and a bit higher before feeling comfortable about moving on.
Another good resource is IMSLP where you can download whole score and study booklets for free. A good example is Daniel Gottlob Turk's Study book which has dozens of exercises in many keys.
Have a look and you'll have an endless supply of material to learn from if you search well enough.