Hi Dennis:
A great way to meet Lilo and her mischievous pal Stitch is to reserve breakfast at
'Ohana's Best Friends Breakfast with Lilo & Stitch. You can receive a visit from Lilo and Stitch and enjoy breakfast served family-style with eggs, bacon, and sausages, among other foods.
If you want to meet the duo in the Parks, I've found that Stitch is easier to find in the Parks than Lilo. Stitch has been known to make appearances at all of the Parks on occasion. When you get to the Parks, pick up a complimentary Times Guide. Along with providing information regarding show times, parades, and special events, the Times Guides generally include character greeting times and locations. You can also stop by guest relations at any of the theme parks and ask them to call the "character hotline" for you. The character hotline will be able to tell you if, where, and when any particular character will be in the parks that day. I also recommend you check out the Stitch's Great Escape attraction, even though you won't meet Stitch in the attraction, you'll get an up close glimpse of one of your favorite characters.
Enjoy your vacation.