As for storing baby clothes to pass on to relatives or friends, there are a few things you should know. First, like big girl clothes, baby clothes also go in and out of style. Depending on how long your sister/friend/neighbor takes, your clothes may or may not be something that she wants. Second, especially for little teeny tiny clothes, she is likely to get showered with lots just like you were. Gift givers love to shower with newborn through six month sizes, and these are the sizes the babies tend to grow out of the quickest. So you fill up your baby’s closet with lots of clothes they almost don’t have time to wear!
And third, be aware that after storing for any length of time, you’ll see invisible stains reappear (like magic, only in a bad way) on your used baby clothes. They can be removed by washing with enzymatic cleaners (Borax) and spending some time outside in bright sunshine, but many a mom has opened bags of stored clothes to think they were all ruined! Just be prepared to spend the time cleaning them up before you give them away if you are storing them.
As far as how best to store them, first ASK your sister/friend/neighbor if she wants them. It may be too much pressure for her to make that commitment yet, and you are under no obligation to pass on the whole lot to her, and you still don’t know if she would even have the same gender child that you did! If she says she does want them, see if she wants to take over the burden of storage. If not and you are still generously offering to store them for her, the best method is probably in SpaceBags. If you don’t know what those are, take a trip to Bed Bath and Beyond and buy a large pack of them.
Finally, set a limit of some kind to guide you. Once kids get in to the twos and threes, many of your child’s clothes may be worn so that you wouldn’t pass them on. Enjoy your little sweetheart in his or her teeny tiny duds for a year, or two, and then start teaching them the valuable lesson of parting with things they no longer need.