A friend gave me this tip when I put my first baby onto formula and I am using it now with my second - you don't have to warm formula before serving it. I steralise my bottles at night and add boiled water to them. I put the teats in and caps on and leave the bottle out on the bench overnight so that the water has time to cool. When I use the bottle the next day I add the formula just before I give it to my baby. He has been served bottles at room temperature from the start and always likes them. There is no issue with bacteria forming because the formula is added immediately before serving. If he doesn't drink the whole bottle I throw the rest out. When I go out I don't have to find somewhere to heat the bottle before I can give it to him. I don't have to carry the bottles in a cooler bag to keep the cool because I carry the bottle and the formula separately. When winter comes I will warm the bottle for about 15 seconds in the microwave just to take the chill off. Does anyone have any other useful tips for feeding?