reward chart

so, my sweet used to be 2 year old entered the world of 3 with full force. he is still sweet and funny and a good listener, most of the time, but he has really been testing his limits. So after doing a lot of looking around, I decided to start him a reward chart. I chose to do a tic tac toe grid. the sheet has four rows of four grids. he gets to put a sticker in a box for things like picking up his toys without being asked, using his nice voice and not the screaming one ( please and thank you is great..but not when it's being screamed at you) and just following directions the first time I ask. when he fills a grid he gets to pick a treat. anything from a cookie or fruit snack to a sticker and extra time at the park. when he fills up two rows, then he gets to either get extra tv time or a trip to target to pick out a new hot wheel. and then for filling the entire page he gets to pick a fun trip like pump it up, the zoo or a lunch date to where ever he chooses. within reason of course. it seems to be working. it's nice to see him so excited about his accomplishments. So i was wondering if any of my other mommy friends out there have had to start similar charts or what do you guys do for rewarding good behavior?
Since I haven't blogged in awhile, Some other things going on with us...we had some family photos taken last month, we were without a computer for a week or so, Riley is doing great with potty training..if only I could get him to poop on the potty. he stays dry...any helpful hints would be greatly appreciated. I know once he does it he will be good to go.. I have been searching for a preschool for him for a few months now, I am having a hard time finding one with an extended birthday date. The only one I found we are on a waiting list for because the class is only 8 kids and it's full. and he needs to be fully potty trained to go. almost there, except for the poop.I am off to sew a fleece hat to go with riley's Halloween costume. he has been telling me all week that he really wants to go trick or treating and driving me crazy! is this what my parents felt like during holidays? and this morning he told us that he really needed a cookie, really pathetic and weak like. ( it didn't work). until next time!