A family tree is not a family history without the stories. Record the wonderful stories from the elders in your family. Even better, video them!
Record the date and full names of the persons and the relationship to you on the video.
Copy or scan old pictures of your relatives. (And be sure you know who they are! “Fred” written on the back of a photo won’t help much, but “Fred Last Name” and the date, location and context will). Using a high quality photocopier works well if a scanner isn’t available. At the very least take photos of the old photos.
Organize your digital photos and videos into folders by surname, making them easier to find later.