Eating Rice Cereal

The doctor said Thomas could eat the baby rice cereal at 4 months old. She said to try feeding him 1 or 2 spoons at first. I tried feeding him, but he kept sticking his tongue out. At 4-1/2 months, he finally is eating it a little, but the rice cereal keeps dripping out of his mouth afterwards. At least some of it is going in though. I read some articles saying that we should wait until at least 6 months to feed rice cereal to babies, and some saying it's ok to feed at 4 months. I'm not sure which is correct, but I'm hearing more people saying at 4 months. Since my doctor said it's ok to feed Thomas, I listened to her. She also said to start feeding him the baby food at 5 months, which is in 2 more weeks. She said if I try out new food, I should wait between at least 3 days to try feeding Thomas each new food, just in case he's allergic to one of the food.