My advice is to give lots of directions! Make sure it is VERY organized and to have a procedure if they forget. I always had the directions posted at each center and if they didn't understand them, they knew 3B4ME (three classmates before they came to me). I kept the same type of centers every week too, so they got used to them (like spelling, computer, phonics, etc.) then just changed the activity. This helped from them coming to me and asking me a zillion questions during guided reading. Also, I made my guided reading very independent, and just retaught everything a lot in the beginning of the year and by the end of the year they didn't need me at all! Hope this helps.
