Look at Their eBay Histories.

If the people you’re buying presents for use eBay, and you know their eBay usernames, then you can take a look at what they’ve been buying to see what they might want. To look at a user’s history, just click ‘Advanced Search’ on the main page, then Find a Member on the left-hand menu. Type in their username and you should reach their user page, complete with all the item numbers of things they have bought. Just paste any item number into the eBay search box to see what the item was. That should give you a few ideas!