It's great to open them as they are received I think, as then you can thank the person who gave it and know who it came from. But I like to be there greeting the guest and making sure my DS says thank you for the present. My pet hate is when there are kids everywhere and the child runs up grabs the present & runs off....then it's left on the ground somewhere because of all that's going on and the parent doesn't even acknowledge its been given or know who it came from......that really annoys me.